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EXCHANGE 




The Preparation and Decomposition of 
Tetrathionates 



DISSERTATION 



PRESENTED IN PARTIAL FULFILLMENT OF THE REQUIRE- 
MENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 
IN THE GRADUATE SCHOOL OF THE OHIO 
STATE UNIVERSITY 



BY 



WALTER SCOTT 



THE OHIO STATE UNIVERSITY 
1920 



The Preparation and Decomposition of 
Tetrathionates 



DISSERTATION 

PRESENTED IN PARTIAL FULFILLMENT OF THE REQUIRE- 
MENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 
IN THE GRADUATE SCHOOL OF THE OHIO 
STATE UNIVERSITY 



BY 



WALTER SCOTT 



THE OHIO STATE UNIVERSITY 
1920 



**< 



TABLE OF CONTENTS 
Sodium Tetrathionate : 

Bibliography. Preparation, (I) Method of Klobukow Modified; (II) Method of 
Sander. Analysis for Sulphur When Precipitated by Addition of Absolute Alcohol. 
Qualitative Tests. Comparative Analyses for Purity. Determination of Water of 
Crystallization. Behavior of Hydrous Salt When Exposed to Air Under Certain Con- 
ditions. Suggested Method for Preparation. 

Barium Tetrathionate: 

Bibliography. Preparation, (I) Previous Methods Used; (II) General Procedure 
of Method Used; (III) Preparation of Barium Thiosulphate; (IV) Difficulties En- 
countered. Comparative Analyses for Purity. Water of Crystallization. Behavior 
of the Hydrous Salt when Exposed to Air. Suggested Method for Preparation. 
Qualitative Decomposition. Quantitative Decomposition, (I) Preliminary; (II) De- 
scription of Apparatus; (III) Procedure; (IV) Purification of Bromine; (V) Prepara- 
tion of Sodium Hypobromite; (VI) Blank Experiment; (VII) Results in Table XI. 
Quantitative Decomposition Including the Analysis of the Filtrate. 

Crystallographic Study of Sodium and Barium Tetrathionates : 

Bibliography. Experimental, (I) Sodium Tetrathionate, (II) Barium Tetra- 
thionate. 

Zinc Tetrathionate: 

Bibliography. Preparation, (I) Previous Methods Used; (II) General Procedure 
of Method Used; (III) Preparation of Barium Tetrathionate; (IV) Preparation of Zinc 
Sulphate. Qualitative Decomposition. Quantitative Decomposition, (I) Descriptive; 
(II) Procedure. Quantitative Decomposition Including the Analysis of the Filtrate. 

Nickel Tetrathionate: 

Bibliography. Preparation, (I) General Procedure of the Method Used; (II) 
The barium tetrathionate and Nickel Sulphate Used. Qualitative Decomposition. 



INTRODUCTION 

Tetrathionates and tetrathionic acid were first prepared by Fordos 
and Gelis in 1842. They were making anaylses of a great number of 
commercial salts, then called "hyposulphites," in order to see if they had 
the same composition. 

In the course of the analysis they attempted to oxidize a solution of the 
salts with iodine in order to convert the sulphur to sulphate. Instead of 
forming a sulphate, a new compound of sulphur was formed and which 
proved on analysis to have the general formula M // S 4 Oe. Since the dis- 
covery of the tetrathionates much work has been done on them and the 
results obtained are not in agreement. The principal reason for this 
seems to be that the tetrathionates were prepared from Wackenroder' s 
solution, which was not of uniform composition. 

The object of the present investigation was to get some definite data 
on some of the tetrathionates, and to further study their decomposition 
quantitatively under the same conditions. 

SODIUM TETRATHIONATE 

BIBLIOGRAPHY 

Fordos and Gelis, Ann. Chim. phys., (3) 6, 486, (1842). 
Jour. f. prak. Chem., 28, 473, (1843). 
Compt. rend., 2, 920, (1843). 

Sodium tetrathionate was prepared by the action of sodium thiosulphate on iodine. 
The sodium thiosulphate was dissolved in water and the iodine added a little at a time 
until there was a slight iodine color remaining. They also stated "That the liquid 
contained neither sulphates, sulphuric acid nor any salt which is precipitated by baryta." 
Fordos and Gelis, Ann. chim. phys., (3) 8, 351, (1843). 

Sodium tetrathionate was prepared by the action of ferric chloride on sodium 
thiosulphate. 

2Na 2 So0 3 + 2FeCl 3 = 2FeCl 2 + 2NaCl + Na 2 S 4 O 6 

All ferric salts behave in a similar way. 
Fordos and Gelis, Ann. chim. phys., (3) 13, 402, (1845). 

Sodium tetrathionate was prepared by the action of auric chloride on sodium 
thiosulphate. 

Kessler, Jour. f. prak. Chem., 47, 34, (1849). 

Pogg. Ann. Phys. Chem. 74, 255, (1849). 
Sodium tetrathionate was prepared by adding cupric chloride dropwise to a con- 



6 

centrated solution of sodium thiosulphate until the cuprous chloride had separated 
and the solution had a light blue color. It was filtered, and alcohol added to the filtrate 
whereby the sodium tetrathionate was precipitated. 

Kressler also prepared the salt by two other methods. 

(a) By the addition of an equivalent amount of sodium carbonate to a solution of 
tetrathionic acid, and then adding alcohol. 

(6) By mixing equivalent solutions of sodium sulphate and lead tetrathionate, 
filtering and then adding alcohol. 

The tetrathionic acid and lead tetrathionate were prepared by the method of Fordos 
and Gelis. (loc. cit.) 

Sonstadt, Chem. News, 26, 99 (1872). 

Sodium tetrathionate was prepared by mixing solutions of sodium thiosulphate 
and potassium iodate and then adding hydrochloric acid. 

6Na 2 S 2 O 3 + KIO 3 + 6HC1 = 3Na 2 S 4 O 6 + KI + GNaCl + 3H,O 

Citric and tartaric acids were used instead of hydrochloric and similar results were 
obtained. 

Sonstadt suggests the use of pure sodium thiosulphate to determine pure iodine, as 
pure iodine will not liberate any sulphur from pure thiosulphate solution. 

Lunge, Ber., 12, 404, (1879). 

In experimenting with the action of hypochlorite on thiosulphate, having the 
thiosulphate in excess, the principal reaction was found to be 
2Na 2 S2O 3 + C1 2 = Na 2 S 4 O 6 + 2NaCl 

Other reactions occur. 

Klobukow, Ber., 18, 1871, (1885). 

Sodium tetrathionate was prepared by the action of iodine on sodium thiosulphate. 
The sodium thiosulphate was finely pulverized in a mortar and a small amount of water 
added to make a paste. Finely pulverized iodine was added a little at a time, grinding 
thoroughly after each addition, until the iodine was in slight excess which may be told 
by the appearance of the yellow color. Pour the syrupy liquid into a beaker and add 
alcohol, whereupon the tetrathionate salt is immediately precipitated as a snow-white 
crystalline precipitate. In case the iodine color disappears during the grinding, a little 
more iodine should be added until there is a permanent iodine color remaining. By 
working under the above conditions they believe there was not an excess of alkali thio- 
sulphate present, nor did any decomposition occur liberating sulphur dioxide. After 
two or three hours standing, the mixture was filtered and the precipitate washed with 
alcohol until all the iodine and iodide had been removed. The precipitate was dis- 
solved in lukewarm water, reprecipitated by the addition of alcohol, filtered, and placed 
in a vacuum desiccator over sulphuric acid to dry. 

Villiers, Compt. rend., 108, 402-03, (1889). 

Ber., 22, R. 222, (1889). 

Sodium tetrathionate was prepared by passing sulphur dioxide through a solution 
of sodium thiosulphate. 



4- 3SO, = Na 2 S 4 O 6 + Na 2 S 3 O 6 

Norris and Fay, Amer. Chem. Journ., 18, 703, (1896). 

Hydrochloric acid was added to a solution of selenious acid, and then an excess 
of sodium thiosulphate. The excess of sodium thiosulphate was taken up with iodine. 
SeO 2 + 4Na 2 S2O 3 = 2Na 2 S 4 O 6 + Se + 2Na 2 O 

The reaction is quantitative. 

Nabl, Ber., 33, 3554, (1900). 

Sodium tetrathionate was prepared by the action of hydrogen peroxide on a solu- 
tion of sodium thiosulphate. 

2Na 2 S20 3 + H 2 2 = Na 2 S 4 O 6 + 2NaOH 

The sodium hydroxide must be removed as soon as it is formed or there is also formed 
in the solution, sulphite, thiosulphate and sulphate. 

He withdraws his previous statement as to the action of hydrogen peroxide on a 
solution of sodium thiosulphate. Ber., 33, 3093, (1900). 

Nabl, Monatshefte f. Chem., 22, 737, (1901) 

Sodium tetrathionate was prepared in the same way as in the above article. If 
the alkali is not neutralized, the oxidation of the thiosulphate is only 25% complete 
and there is also formed dithionate and sulphate as well as tetrathionate. 

Willstatter, Ber., 35, 1831, (1903). 

He states that the action of hydrogen peroxide on a solution of sodium thiosulphate 
is 

2Na 2 S2O 3 4- 4H 2 O 2 = Na 2 S 3 O 6 + Na 2 SO 4 + 4H 2 O 

This is in disagreement with the results of Nabl (loc. cit.} 
Thatcher, Zeitschr. f. phys. Chem., 47, 641, (1904). 

Sodium tetrathionate was prepared by the electrolytic oxidation of sodium thio- 
sulphate in neutral solution, using platinized electrodes with a definite anode potential 
difference. He considered the reaction to be a secondary rather than a primary one, 
probably brought about by the oxygen which is formed during the electrolysis together 
with the aid of the platinized electrodes. 

Primary: 2S*O 3 " + 2F = S 4 O 6 " 

Secondary: O"4- 2F = 1/2 O 2 

y 2 0, 4-2S2(Y'= S 4 6 "+0" 
Abel, Monatshefte f. Chem., 28, 1239, (1907). 

Sodium tetrathionate was prepared in two ways. 

(a) By the action of hydrogen peroxide on sodium thiosulphate in acetic acid 
solution. 

H 2 0, + 2Na 2 S,0 3 -f 2CH 3 COOH = Na 2 S 4 O 6 4- 2CH 3 COONa 4- 2H 2 O 

(b) By the action of hypoiodite on thiosulphate in acetic acid solution. 

10' -f 28,03"+ 2H' = S 4 6 "-f H 2 + I' 



Fromm, Ber., 40, 3397, (1908). 

The sodium tetrathionate was prepared by the method of Klobukow (loc. cit.}. 
He analyzed the salt by determining the barium sulphate; also by determining the so- 
dium sulphate. The water of crystallization was determined by drying the salt at 
110 C. 

Stiasny and Das, Jour. Soc. Chem. Ind., 31, 753, (1912). 

Sodium tetrathionate was prepared by the action of potassium dichromate and 
sulphuric acid on a solution of sodium thiosulphate. They give three possible re- 
actions, but in only one is the tetrathionate formed. The extent to which each of these 
reactions takes place depends on the dilution and the amounts of acid and thiosulphate 
present. 

Vanino and Schinner, Ber., 46, 1776, (1914). 

Sodium tetrathionate was prepared by the method of Fordos and Gelis (loc. cit,}. 

About 50 grams of pure sodium thiosulphate (Na2S2Os . 5H2O) and 25 grams of 
iodine were finely pulverized in a mortar, placed in a 500 cc. flask and treated with 50 
cc. of absolute alcohol. The pasty mass (at the ordinary temperature) was kept in 
constant motion by means of a shaking machine until complete decolorization, requir- 
ing about two days. Pulverized iodine was now added until permanent coloration, 
and then 100 cc. of absolute alcohol. The separated salt was washed with a mixture of 
absolute alcohol and ether until the wash liquid after the addition of some water and 
ammonia no longer became turbid on the addition of silver nitrate. After that the salt 
was dried in the air between filter paper, then placed in a beaker and dissolved in 50 cc. 
to 60 cc. of distilled water. A small amount of iodine dissolved in alcohol was added 
to this solution until there was a permanent coloration of iodine, then 350 cc. of a mix- 
ture of absolute alcohol and ether. After standing some time the salt was filtered off, 
washed with absolute alcohol-ether, and lastly with ether only. In a short time it 
lost the odor of ether and was then placed in a stoppered bottle. 

Sander, Zeitschr. angew. Chem., 28, 273, (1915). 

The tetrathionates of sodium and potassium were prepared by the method of Fordos 
and Gelis (loc. cit.}. 

26 grams of iodine were dissolved in alcohol and into this cooled solution a satur- 
ated solution of 50 grams of sodium thiosulphate (Na2S2Os . SH^O) or 39.5 grams of potas- 
sium thiosulphate (at room temperature) were added 'gradually by means of a drop 
funnel. The decomposition of the thiosulphate occurs immediately with the excess of 
iodine, and the tetrathionate which is formed being insoluble in alcohol separates in 
small crystals. These crystals were filtered off and washed with alcohol until the wash 
liquid was free of iodine and iodide, then dissolved in the least possible amount of water 
and reprecipitated by the addition of alcohol. The crystals were filtered off, pressed 
between filter paper and finally dried over sulphuric acid. 

On analysis the potassium salt was found to be pure and the sodium salt to be 
impure. The methods of analysis used were: 

1. By calcination and obtaining the sulphate. 



9 

2. By oxidation with mercuric chloride and titrating with standard NaOH. 

3. By oxidation with bromine water and precipitating as barium sulphate. 

4. By reduction with nascent hydrogen and determining the amount of hydrogen 
sulphide. 

Related Articles 

Plessy, Ann. chim. phys., (3) 20, 162, (1847). 

He claimed to have discovered a new series of sulphur acids by the action of sul- 
phur monochloride on sulphurous acid. Salts were prepared from the acids by neutral- 
ization with carbonates. 

Fordos and Gelis, Ann. chim. phys., (3) 22, 66, (1848). 

They were unable to verify the results of Plessy (loc. cit.}. 

Mendeleeff, Ber., 3, 870, (1870). 

Prin. 0} Chem. II, 284, (1905). 

He gives the persulphidic structure to the tetrathionates. Debus, Jour. Chem. 
Soc., 53, 351, (1888) states that Mendeleeff adopted the structure of Blomstrand (Chem. 
d. Jetzzeit, 158). 

Persulphidic Structure 
H-O-SO 2 
S 

s 

H-O-SO 2 
Gutman, Ber., 37, 1728, (1905). 

He prepared sodium tetrathionate by the method of Fordos and Gelis (loc. cit.} 
and Klobukow (loc. cit.}. He suggested the peroxidic structure for tetrathionates. 
Peroxidic Structure 

Na-0-S 

S 

O 
Na-O-Sg 

Gutman, Ber., 39,3614, (1907). 

He investigated the validity of the results obtained by Fordos and Gelis (loc. cit.} 
and Kessler (loc. cit.} on the action of sodium hydroxide on sodium tetrathionate. 

Gutman, Ber., 40, 300, (1908). 

An investigation of the action of carbonates of sodium, potassium and lithium on 
sodium tetrathionate. 

Debus, Jour. Chem. Soc., 53, 278, (1888). 

Ann. Chem., 244, 76, (1888). 

He prepared a mixture of potassium thionates by passing sulphur dioxide through 
a potassium thiosulphate solution. 



10 

9SO 2 = K 2 S 5 6 + K 2 S 4 O 6 + 4K 2 S 3 O 6 
Wackenroder's solution was also prepared, the acidity determined, and an equiva- 
lent amount of potassium acetate added (assuming pentathionic acid). The solution 
was evaporated at the ordinary temperature and potassium pentathionate obtained. 
He further states "The use of potassium acetate instead of potassium hydroxide is 
advantageous because all the acid of Wackenroder's solution can be converted into the 
potassium salt, and the hydric acetate which is set free tends to prevent the decompo- 
sition of the potassium pentathionate. The mother liquors contain much potassium 
pentathionate and tetrathionate." 

The salt obtained above was analyzed by 

(a) Oxidation with nitric acid and precipitation with barium chloride. 

(b) Oxidation with bromine water and precipitation with barium chloride. 
The results of the analysis gave results close to the generally accepted ratios of 

potassium to sulphur, 2:5. 

On page 356 a probable structure for tetrathionates is given. 
K-S-S0 2 
O 
S 
K-0-S0 2 

Chancel and Diacon, Compt. rend., 1, 710, (1863). 

Jour. f. prak. Chem., 90, 55, (1863). 

The tetrathionates of copper and lead were prepared. Tetrathionic acid was 
also prepared by adding sulphuric acid little at a time to a mixture of lead thiosulphate 
and lead peroxide. 

2PbS2O 3 + PbO 2 + 2SO 3 = PbS 4 O 6 + 2PbSO 4 
Vortmann, Ber., 22,. 2311, (1889). 

Arsenic is completely precipitated by sufficient excess of thiosulphate; in presence 
of arsenious acid there is obtained in the filtrate principally tetrathionic acid besides 
a trace of pentathionic acid. Sulphuric acid is not formed or only in traces. If too 
little sodium thiosulphate is present, a part of the arsenious acid remains in solution, 
and the reaction proceeds according to the equation: 

As 2 O 3 + 9H 2 S 2 O 3 = As 2 S 3 -f 3H 2 S 4 O 6 + 3SO 2 + 6H 2 O 

Two thirds of the sulphur present should go over into the tetrathionate. Two 
experiments gave 16.08% and 15.46%; sulphur instead of 17.14%, calculated from the 
sodium thiosulphate. 

Marshall, Jour. Soc. Chem. Ind., 16, 396, (1897). 

The tetrathionates of potassium and ammonium were prepared by the action of 

persulphates on thiosulphates. 

KaSoOs + 2K 2 S20 3 = K 2 S 4 6 + 2K 2 SO 4 
(NH 4 ) 2 S20 8 + 2BaS20 3 = (NH 4 ) 2 S 4 O + 2BaSO 4 



Mackenzie and Marshall, Jour. Chem. Soc., II, 93, 1726, (1908). 



11 

Potassium tetrathionate was prepared by the action of potassium persulphate and 
barium thiosulphate. 

= K 2 S 4 O 6 + 2BaSO 4 



PREPARATION 

Sodium tetrathionate was first prepared by following the method given 
by Biltz and Biltz (Ubungbeispeile aus der unorgan. Experimentalchemie, 
122): "50 grams of sodium thiosulphate, 26 grams of iodine and 5 grams 
of water are pulverized in a mortar to a complete homogeneous light brown- 
ish yellow paste. In a short time the paste is washed into an Erlenmeyer 
flask using alcohol as the wash liquid. After about three hours the pre- 
cipitated sodium tetrathionate is filtered off using suction and washed 
with alcohol until the filtered alcohol is free of iodine. The crude product 
is dissolved in 20 grams to 25 grams of lukewarm water, filtered, and 
alcohol added about 10 grams at a time until about 50 grams have been 
added. After about ten hours, during which time the mixture has been 
kept away from the air either in an Erlenmeyer flask or a vacuum desic- 
cator, it is filtered using suction and the crystals washed with alcohol, 
and dried in a sulphuric acid desiccator. The crystals are colorless and 
in aggregates. Yield about 20 grams." 

The above method is that of Klobukow (loc. cit.} somewhat modified; 
practically the same as given in Biltz, Hall and Blanchard (Laboratory 
Methods of Inorganic Chemistry, 1 32) ; and somewhat similar to that given 
in Rose-Finkener (Handb. der analyt. Chem., 6 Aufl., II, 629). 

In following the above directions it was found that the yields were low 
and variable, being from 20% to 40% of the theoretical. 

In order to determine if the yield of the sodium tetrathionate could be 
increased, a series of experiments were made by precipitating the salt from 
alcoholic, alcohol-ether, and water solutions and allowing them to stand 
over night, or to cool them for two or three hours with a mixture of salt 
and ice. 

I METHOD OF KLOBUKOW (MODIFIED) 

The conditions under which the results in Table I, A, B, and C were 
obtained are as follows: 

.">() grams of C. P. Na 2 S 2 O3.5H 2 O were finely pulverized in a mortar, 
5 cc. of alcohol added and then 26 grams of resublimed iodine, which 
had been previously finely pulverized, were added a little at a time and 



12 

thoroughly mixed after each addition. (Whenever the term alcohol is 
used in this paper, unless otherwise specified, is meant alcohol containing 
93% alcohol by weight or about 95% alcohol by volume). The contents 
of the mortar were transferred to a beaker using alcohol as the wash liquid 
to completely remove all the residue and then allowed to stand from two 
to three hours. It was then filtered through a Biichner and washed free 
of iodine and iodide by means of alcohol and then sucked dry ; redissolved 
in warm water, filtered and reprecipitated as specified in A, B, and C of 
Table I. 

II METHOD OF SANDER (See D of Table I) 

Sodium tetrathionate was prepared according to Sander (loc. cit.) except 
that absolute alcohol-ether (1:1), by volume, at room temperature was 
used instead of cooled absolute alcohol. The precipitated sodium tetra- 
thionate was redissolved in the smallest amount of warm water, filtered, 
and added to a mixture of absolute alcohol-ether (1:1) and allowed to 
stand over night. 

TABLE I. 
A. Precipitation by allowing to stand over night. 

Cc. of water used Temperature 

to dissolve the of water Precipitated Cc. Yield 

sodium tetrathionate C. from used in % 

25 20 alcohol 60 20 

18 50 alcohol 60 50 

18 45 alcohol 60 35 
17 50 absolute alcohol 100 65 

17 50 absolute 

alcohol-ether 100 65 

B. Precipitation by cooling with a mixture of salt and ice to 10 

for three hours. 

19 45 alcohol 60 65 
14 55 absolute alcohol 60 65 
16 50 absolute alcohol 75 70 
14 55 absolute 

alcohol-ether =150 70 

C. Precipitation by cooling the saturated water solution to 5 for 

three hours. 

18 50 water 18 40 

D. Precipitation according to Sander. 
14 50 absolute 

alcohol-ether = 500 60 



13 

By reducing the volume of water in which the sodium tetrathionate is 
redissolved before precipitation, and warming it to increase the solubility 
and using absolute alcohol or absolute alcohol-ether (1:1) instead of alco- 
hol, the yield was practically doubled. It was found that a fair yield may 
be obtained from a water solution by cooling with a freezing mixture of 
salt and ice. 

Somewhat better yields were obtained by cooling the solutions rather 
than by allowing them to stand over night, unless they were placed out 
of doors when the weather was cold, and under such conditions the yield 
would sometimes run as high as 80%. 

ANALYSIS FOR SULPHUR 

In order to get an idea of the purity of the sodium tetrathionate which 
had been precipitated from a concentrated water solution by the addition 
of absolute alcohol, a number of experiments were run the results of which 
are shown in Table II, A, B, and C and in which the sulphur found was 
compared with the theoretical amount of sulphur, assuming the sodium 
tetrathionate to be Na 2 S 4 O 6 . 2H 2 O. 

Procedure: 0.100 gm. to 0.150 gm. of sodium tetrathionate which had 
been precipitated from alcohol solution and thoroughly dried between 
filter papers were dissolved in water and bromine water added to distinct 
bromine coloration. 

Na 2 S 4 O 6 + 14Br + 10H 2 O = Na 2 SO 4 + 3H 2 SO 4 + 14HBr 

The solution was then boiled until the bromine had been driven off 
and precipitated with barium chloride. 

The conditions under which the sulphate ions were precipitated in this 
series of experiments and all others which follow were : two or three drops 
of concentrated hydrochloric acid were added to the solution, then heated 
to boiling and barium chloride solution (made by dissolving 25 gm. of 
BaCl 2 .2H 2 O in one liter of water) added slowly with constant stirring 
until about one and one-half times the theoretical amount had been added. 
The solution was allowed to stand for one-half hour and then filtered 
through an ashless filter. 

The concentration of the sulphate ion before precipitation was kept so 
that the adsorption by the barium sulphate after precipitation was prac- 
tically equal to its solubility, viz., about one gram of barium sulphate from 
a liter of solution. 

The Results: The results of this series of experiments are recorded in 



14 

Table II. In trials 1 to 5 inclusive, the sodium tetrathionate solution 
was contained in a beaker and the bromine water was dropped into it 
from a pipette, stirring constantly. 

In trials 6 to 9 inclusive, the sodium tetrathionate solution was con- 
tained in a closed Erlenmeyer flask and the bromine water was added from 
a drop funnel. In trial 10 the tip of the pipette was placed below the 
surface of the sodium tetrathionate solution contained in a beaker when 
the bromine was added, stirring constantly. 

TABLE II 

A. The sodium tetrathionate solution contained in a beaker and the 
bromine water dropped in from a pipette. 



Sodium tetra- 
thionate 
used 
Gm. 


BaSO 4 calc. 
from sodium 
tetrathion- 
ate taken. 
Gm. 


Sulphur calc. 
from sodium 
tetrathionate BaSO* 
taken found 
Gm. Gm. 


Sulphur 
found 
Gm. 


Error 

BaS04 
Gm. 


Error 
in 
Sulphur 
Gm. 


1. 


0. 


1X)15 


0.3094 


0.0425 





.3049 


0.0419 


-0 


0045 


-0 


.0006 


2. 


0. 


1016 


0.3097 


0.0426 





.2999 


0.0412 


-0 


.0098 


-0 


.0014 


3. 


0. 


1503 


0.4582 


0.0629 





.4526 


0.0622 


-0 


.0056 





.0007 


4. 


0. 


1508 


0.4597 


0.0632 





.4533 


0.0623 


-0 


.0064 


-0 


.0009 


5. 


0. 


1515 


0.4618 


0.0634 





.4569 


0.0628 


-0 


.0049 


-0 


.0006 



B. The sodium tetrathionate solution contained in a closed flask and the 

bromine water added from a drop funnel. 

6. 0.1522 0.4639 0.0637 0.4580 0.0629 -0.0059 -0.0008 

7. 0.1514 0.4615 0.0634 0.4619 0.0634 +0.0004 0.0000 

8. 0.1508 0.4597 0.0632 0.4576 0.0629 -0.0021 -0.0003 

9. 0.1506 0.4591 0.0631 0.4573 0.0628 -0.0018 -0.0003 

C. The sodium tetrathionate solution contained in a beaker and the 
bromine water added from a pipette with the tip below the surface 

of the solution. 
10. 0.1510 0.4603 0.0633 0.4584 0.0630 -0.0019 -0.0003 

The results of Table II show that the sodium tetrathionate precipitated 
by the addition of absolute alec hoi is quite pure. Also, in the oxidation 
of the solution of sodium tetrathionate, certain precautions must be ob- 
served in order to prevent loss of sulphur. 

QUALITATIVE TESTS 

Samples of sodium tetrathionate precipitated from alcohol, alcohol- 
ether, and water solutions were dissolved in water and tested qualitatively, 
about 10 cc. of the solution being used for each test. 



15 

Solutions added. Results 

Barium chloride In somewhat concentrated solutions a slight cloudiness 

was produced. 

Lead acetate None. 

Iodine Small part of a drop gave coloration. N/10 used. 

Mercurous nitrate Yellow precipitate. 
Dilute potassium 

permanganate Red color. No brown precipitate. 

Ferric chloride Slight coloration in somewhat concentrated solutions. 

In dilute solutions the salts dissolved clear, while in more concentrated 
solutions there was a slight cloudiness. All sodium tetrathionate solu- 
tions were neutral to litmus. 

For tables showing the characteristic tests for sulphur salts see 

Lieb, Ann., 207, 90, (1881). 

Zeitschr. phys. Chem., 47, 652, (1904). 

Prescott and Johnson Qual., Chem. Anal., 7th Ed., 326. 

In the above tests the following would be indicated: Barium chloride 
in presence of hydrochloric acid would detect presence of sulphates. 

Lead acetate would detect presence of iodides. 

Iodine would detect the presence of sulphites and thiosulphates. 

Mercurous nitrate: dithionates no precipitate; sulphites, thiosulphates, 
and trithionates a black precipitate; tetrathionates and pentathionates 
a yellow precipitate. 

Dilute potassium permanganate; dithionates and trithionates a red 
precipitate; tetrathionates and pentathionates bleach. 

The qualitative tests show possible traces of free sulphur, and some 
thiosulphate, the salt crystallized from water solution showing the least. 

Pozzi-Escot, Bui. soc. Mm., (4), 13, 401, (1913) gives a very delicate 
test for thiosulphates, sulphites and polythionates not giving the reaction. 

Take 2 cc. of solution containing the thiosulphate and add 2 cc. of a 
ten per cent ammonium molybdate solution ; then add 5 cc. of concentrated 
sulphuric acid. A blue ring will form between the layers, which may be 
more readily seen by using a white background. He states .00005 gm. 
of sodium thiosulphate may be detected. 

In order to test the above .0020 gm. of sodium thiosulphate was dis- 
solved in 500 cc. of water and 2 cc. of the solution tested. It gave a blue 
ring between the layers after about three minutes, using a white back- 
ground. 



16 
COMPARATIVE ANALYSES FOR PURITY 

A comparison of the purity of the various samples of .spdium tetrathio- 
nate was made by determining the amount of sodium sulphate, shown in 
Table III, A, B, C, and D; and also by determining the total sulphur as 
barium sulphate, shown in Table IV, A, B, C, and D. 

In determining the sodium sulphate it was assumed that the sodium 
tetrathionate had the composition Na 2 S4O 6 .2H 2 O, and when heated de- 
composed into sodium sulphate, sulphur dioxide and water. 

The results in Table III were obtained by weighing out about one gram 
of the sodium tetrathionate in a crucible and heating at first with a very 
low Bunsen flame for a half hour or more keeping the lid on the crucible 
and gradually raising the heat until the full heat of the Bunsen. Then 
it was heated with the partial heat of a blast lamp for five minutes, placed 
in the desiccator, cooled and weighed. 

TABLE III 

A. Sodium tetrathionate prepared by method of Klobukow, modified, dis- 

solved in water and precipitated by addition of absolute alcohol. 

Sodium tetrathionate Na2SO4 

used. calc. Na 2 SO 4 Error in Na 2 SO4. 

Gm. Gm. Found. Gm. 

1.0482 0.4862 0.4883 +0.0021 

1.0055 0.4664 0.4682 +0.0018 
1.0069 0.4670 0.4694 +0.0024 
1.0007 0.4641 0.4668 +0.0027 
1.0017 0.4646 0.4667 +0.0021 
0.7083 0.3285 0.3306 +0.0021 
0.7362 0.3414 0.3435 +.00021 

B. Sodium tetrathionate prepared by method of Klobukow modified, dis- 
solved in water and precipitated by the addition of absolute alcohol- 
ether (1:1). 

1.0081 0.4676 0.4716 +0.0040 

1.0063 0.4667 0.4700 +0.0033 

C. Sodium tetrathionate prepared by the method of Sander dissolved in 
water and precipitated by the addition of absolute alcohol-ether (1:1). 

1.0056 0.4664 0.4760 +0.0096 
1.0094 0.4682 0.4778 +0.0096 

D. Sodium tetrathionate prepared by method of Klobukow modified, dis- 
solved in water and precipitated from the water solution by cooling with 

a mixture of salt and ice. 

1.0038 0.4656 0.4646 -0.0010 

1.0069 0.4670 0.4661 0.0009 



17 

The results given in Table IV were obtained by using the samples of 
sodium tetrathionate as used to obtain the results in Table III, and in 
the calculations the same assumption was made as to the composition 
of the sodium tetrathionate, viz., Na 2 S 4 O6.2H 2 O. 

About .1500 gm. of the sodium tetrathionate were weighed, dissolved 
in water, and bromine water added from a .pipette, the tip of which was 
below the surface of the solution while the bromine water was added, 
stirring constantly until there was a distinct coloration due to the bromine 
and then the excess of bromine boiled off. 

The same precautions were observed in the precipitation of the barium 
sulphate as in Table II. 

TABLE IV 

A. Sodium tetrathionate prepared by the method of Klobukow modified, 
dissolved in water and precipitated by the addition of absolute alcohol. 

Sodium tetra- BaSO4 Sulphur BaSO4 Sulphur Error Error in 

thionate used. calc. calc. found. found. in BaSO4 sulphur. 

Gm. Gm. Gm. Gm. Gm. Gm. Gm. 

0.1529 0.4661 0.0640 0.4646 0.0638 -0.0015 -0.0002 
0.1668 0.5085 0.0699 0.5065 0.0696 -0.0020 -0.0003 

B. Sodium tetrathionate prepared by the method of Klobukow modified, 
dissolved in water, and precipitated by the addition of absolute alcohol- 
ether (1:1). 

0.1547 0.4716 0.0648 0.4672 0.0642 -0.0044 -0.0006 
0.1560 0.4756 0.0653 0.4715 0.0648 -0.0041 -0.0005 

C. Sodium tetrathionate prepared by the method of Sander, dissolved in 
water and precipitated by the addition of absolute alcohol-ether (1:1). 

0.1519 0.4631 0.0636 0.4573 0.0628 -0.0058 -0.0008 
0.1510 0.4603 0.0632 0.4544 0.0624 -0.0059 -0.0008 

D. Sodium tetrathionate prepared by method of Klobukow modified, and 
precipitated from the water solution by cooling with a mixture of salt 

and ice. 

0.1785 0.5441 0.0748 0.5436 0.0747 -0.0005 -0.0001 
0.1515 0.4618 0.0635 0.4611 0.0634 -0.0007 -0.0001 

The results of the analyses of the various samples of sodium tetrathionate 
in Tables III and IV show that the salt crystallized from the water solution 
has the highest degree of purity. However, it might be added that the 
salt crystallized from the water solution would give a positive test for the 
presence of thiosulphates by using the ammonium molybdate sulphuric 
acid test suggested by Pozzi-Escot (loc. cit.) if considerable amount of the 



18 

sodium tetrathionate be used. The samples of sodium tetrathionate 
prepared by the method of Klobukow modified, dissolved in water and 
precipitated by the addition of absolute alcohol or absolute alcohol-ether 
(1:1), or prepared by the method of Sander and precipitated by the addi- 
tion of absolute alcohol-ether, always gave a decided test for thiosulphates 
when the ammonium molybdate sulphuric acid test was applied. 

DETERMINATION OF WATER OF CRYSTALLIZATION 

Fordos and Gelis (loc. cit.) determined the water of crystallization in 
sodium tetrathionate by difference. Fromm (loc. cit.) found it by drying 
the sodium tetrathionate in the air at 110. 

The water of crystallization was determined in the present investi- 
gation by means of a small gas combustion furnace in an atmosphere of 
carbon dioxide, the arrangement being shown in Fig. 1 . The carbon 
dioxide was obtained from a Kipp generator not shown and passed through 
a sodium carbonate solution A, and then through two calcium chloride 
drying columns B. The bottle C and stopcock D were used for conven- 
ience. The asbestos shield K protected the absorption tube L from the 
heat of the furnace. Ordinary copper oxide wire I was used, and the copper 
spiral H was reduced in the usual way by means of methyl alcohol. The 
reduced copper spiral H takes up the free sulphur formed from the de- 
composition of the sodium tetrathionate and decomposes any hydrogen 
sulphide which may form. During any one combustion only a small 
part of the reduced copper spiral H next to the boat G was attacked or 
used by the sulphur. A very small amount of the copper oxide wire was 
reduced, showing that a very little hydrogen sulphide was formed. 

The temperature at which the combustions were carried out was the 
full heat of the gas combustion furnace in which the glass tube was a bright 
cherry red. 

Before making a determination, the furnace was ignited and the train 
swept out with carbon dioxide passing at the rate of two bubbles per second 
until the weight of the calcium chloride absorption tube L was constant 
to within .4 mg. The time required for this was from three to five hours. 

The time required for a determination after placing the sodium tetra- 
thionate in the combustion tube was from three to four hours, which in- 
cluded the gradual heating up of the furnace, the combustion and the 
sweeping out of the train. 



19 




20 

The calcium chloride absorption tube L, after each combustion was 
closed on each side and placed in a large sulphuric acid desiccator for 
one-half hour before each weighing. 

Preliminary to the determination of the water of crystallization in the 
sodium tetrathionate, two combustions were made with some selected 
crystals of C. P. sodium thiosulphate, the results being shown in Table 
V, A. The sodium tetrathionate used in the experiments shown in Table 
V, B, was crystallized from a water solution by cooling with salt and ice 
and dried between filter papers. 

TABLE V 

A. Determination of water of crystallization in hydrous sodium thiosulphate. 

Weight of sodium Weight of sodium Weight of water Weight of water 
thiosulphate taken, tetrathionate taken. found. calc. Error in 

Gm. Gm. Gm. Gm. Gm. 

0.3841 0.1391 0.1394 -0.0003 

0.4852 0.1753 0.1761 0.0008 

B. Determination of water of crystallization in hydrous sodium 

tetrathionate. 

1.1998 0.1414 0.1411 +0.0003 

1.1914 0.1407 0.1401 +0.0006 

In making the calculations for the water of crystallization in hydrous 
sodium thiosulphate and hydrous sodium tetrathionate in A and B of 
Table V, their compositions were assumed to be Na 2 S2O 3 .5H 2 O and Na 2 - 
S 4 O 6 .2H 2 O respectively. 

The results in B of Table V show that each molecule of hydrous sodium 
tetrathionate contains two molecules of water of crystallization. 

BEHAVIOR WHEN EXPOSED TO AIR AT ORDINARY ATMOSPHERIC PRES- 
SURES; TO AIR OVER SULPHURIC ACID AT ORDINARY AND REDUCED 
ATMOSPHERIC PRESSURES 

Klobukow (loc. oil.), Biltz and Biltz (loc. cit.) and Sander (loc. cit.) in 
the preparation of sodium tetrathionate direct to dry the salt over sul- 
phuric acid. Sander (loc. cit.} stated that he was unable to prepare pure 
hydrous sodium tetrathionate, yet he prepared pure anhydrous potassium 
tetrathionate using the same method, drying both salts over sulphuric 
acid. 

In order to determine the behavior of hydrous sodium tetrathionate 
when exposed to the air at ordinary atmospheric pressure, to air over 



21 

sulphuric acid at ordinary and also reduced atmospheric pressures, the 
experiments the results of which are shown in Table VI, A, B, and C 
were made. The sodium tetrathionate was spread out on one of two 
tared watch glasses. 

TABLE VI 

A. Hydrous sodium tetrathionate exposed to air. 

Weight of sodium Loss in weight of 

tetrathionate Time exposed. sodium tetrathionate. 

Gm. Days. Gm.. 

1.0040 0.0000 

1.0045 2 +0.0005 

1.0044 10 +0.0004 

B. Hydrous sodium tetrathionate exposed to air over concentrated 

sulphuric acid at ordinary atmospheric pressure. 

1.0042 0.0000 

1.0035 1 0.0007 

1.0032 2 0.0010 

1.0016 4 0.0026 

1.0011 5 0.0031 

1.0010 6 0.0032 

0.9998 8 0.0044 

0.9982 11 0.0060 

C. Hydrous sodium tetrathionate exposed to air over concentrated 
sulphuric acid at reduced atmospheric pressure (from two to five 

cm. of Hg). 

0.9982 0.0000 

0.9970 2 0.0012 

0.9960 3 0.0022 

0.9789 15 0.0193 

0.9647 27 0.0335 

The results obtained in Table VI, A, show that the weight of hydrous 
sodium tetrathionate is fairly constant in the air, the slight changes shown 
being due to decided changes in the humidity; those in B and C show a 
gradual loss in weight over sulphuric acid, either at ordinary or reduced 
atmospheric pressure. Further, the results show that the dissociation 
pressure of hydrous sodium tetrathionate is of such magnitude that it 
should not be dried over concentrated sulphuric acid for any considerable 
length of time. 

SUGGESTED METHOD FOR PREPARATION 

Weigh out 50 grams of Na 2 S2O 3 .5H 2 O and 26 grams of iodine and pul- 



verize each in separate mortars. To the finely pulverized sodium thio- 
sulphate in the mortar, add approximately 5 cc. of distilled water and 
25 cc. of alcohol and thoroughly mix. Then add the iodine a little at a 
time, thoroughly mixing after each addition, until all has been added and 
there remains a slight excess of iodine. Add 25 cc. of alcohol and allow 
to stand from twenty minutes to one half hour, filter through a Biichner 
using suction, and wash free of iodine and iodide by means of alcohol. 

The absence of iodine may be told by the color of the wash alcohol, 
and the absence of iodide by the addition of a few drops of a dilute solution 
of lead acetate to the wash alcohol. Lead acetate when added to the wash 
alcohol forms a yellow precipitate of lead iodide when an iodide is present, 
and a white precipitate of lead tetrathionate when it is absent. 

The precipitate after it has been sufficiently washed with alcohol is 
sucked nearly dry on the Biichner in order to remove most of the alcohol, 
dissolved in the smallest possible amount of water (15 cc. to 17 cc.), warmed 
to 50 to 60 and filtered through a Gooch using suction into a test tube 
which is placed within a one liter Erlenmeyer filter flask. To this filtrate 
add ten to fifteen drops, or if necessary more, of iodine in alcohol solution. 
There should be a slight iodine coloration. 

The sodium tetrathionate may be precipitated or crystallized from 
the filtrate by the addition of absolute alcohol-ether (1:1) or absolute 
alcohol and allowing to stand over night, or by cooling with a mixture of 
salt and ice. 

(I) Precipitation by ike addition of absolute alcohol-ether or absolute alcohol 

and allowing to stand over night. 

Add the filtrate to a crystallizing dish and then add 100 cc. of absolute 
alcohol-ether (1:1) and place in an empty desiccator (best a vacuum 
desiccator) for at least twelve hours. 

Instead of using absolute alcohol-ether (1:1), 100 cc. of absolute alcohol 
may be used with nearly the same yield. 

(II) Precipitation by the addition of absolute alcohol-ether or absolute alcohol 

and cooling by means of salt and ice. 

Add the filtrate to a small beaker and then add 100 cc. of absolute alcohol- 
ether (1 : 1) and cool by placing in a mixture of salt and ice for two or three 
hours, keeping the beaker covered. Absolute alcohol may be substituted 
for the absolute alcohol-ether as in (I). 

Whether the sodium tetrathionate is precipitated by (I) or (II), it 



23 

should be filtered using suction and sucked as dry as possible, then placed 
between filters and dried. It should then be crystallized from a water 
solution by cooling as this removes practically all the thiosulphate. 

Recrystallization from Water. The dry sodium tetrathionate obtained 
from the absolute alcohol-ether or the absolute alcohol mixtures is dis- 
solved in the smallest amount of water at 50 to 60 in a beaker and 
cooled by a mixture of salt and ice for two or three hours. This will give 
about one half of the sodium tetrathionate dissolved. The sodium tetra- 
thionate precipitated should be filtered off using suction to remove the 
greater part of the water, then placed between filter papers until dry. 
After the salt has been dried, it should be placed in a glass stoppered 
bottle. 

In case it is desired, the greater part of the sodium tetrathionate still 
dissolved in the mother liquor or filtrate may be precipitated by the addi- 
tion of absolute alcohol-ether (1:1) or absolute alcohol. 

Stability of Sodium Tetrathionate. Two different samples of sodium 
tetrathionate crystallized from water and thoroughly dried between filter 
paper were kept in glass stoppered bottles for one and one-half years. 
One sample had a very slight tinge of yellow and when dissolved in water 
showed some turbidity; the other sample remained perfectly white and 
when dissolved in water showed only the slightest trace, of turbidity. 

Sander (loc. cit.) says that solutions of pure tetrathionates may be boiled 
without decomposition. He further states that the presence of sodium 
thiosulphate greatly accelerates the decomposition. 

BARIUM TETRATHIONATE 

BIBLIOGRAPHY 

Fordos and Gelis, Ann. chim. phys., (3) 6, 489(1842). 
Jour.f. prak. Chem., 28, 476(1843). 

Barium tetrathionate was prepared by the action of iodine on barium thiosulphate. 

Barium thiosulphate was mixed with water forming a thin paste and small amounts 
of iodine were added until it just began to color; the excess of iodine and iodide were 
washed out with alcohol. The white powder was dissolved in the smallest amount of 
water possible, filtered and allowed to evaporate. The crystals were more readily 
obtained when absolute alcohol was added to the solution. 

The barium tetrathionate had a bitter taste, was very soluble in water, slightly in 
alcohol, kept at the ordinary temperature in dry air but became yellow in a short time 
in moist air. 



24 

They made an analysis of the salt as follows: A known amount of the salt was 
dissolved in water and oxidized with chlorine. The solution was filtered, and the 
barium sulphate formed was weighed. The sulphuric acid formed during the oxidation 
was precipitated with barium chloride. 

The water of crystallization was found by difference. 

Wackenroder, Archiv. der Pharm., 47, 272, (1846). 

Wackenroder's solution was prepared by passing hydrogen sulphide into a satur- 
ated water solution of sulphur dioxide at room temperature until there was an excess 
of hydrogen sulphide. The solution was then shaken with some oxidized copper turn- 
ings and filtered. This filtrate was immediately completely neutralized with barium 
carbonate and a little barium hydroxide, and after a few hours the solution was ready 
to be used. 

(a) A known weight of the barium pentathionate solution was taken and the barium 
determined by precipitation with sulphuric acid. 

(&) A known weight of the barium pentathionate solution was taken and a solution 
of potassium hydroxide added and the solution evaporated to dryness. The residue 
was dissolved in water, nitric acid added, and the solution boiled. This solution was 
evaporated to dryness, the residue dissolved in water and a solution of barium chloride 
added. The results of the first trial showed the ratio of the barium to the sulphur to 
be 1 : 5.23. In the second trial the ratio of barium to sulphur was found to be 1 : 5. 

Wackenroder, Archiv. of Pharm., 48, 140, (1846). 

This was a continuation of the previous article and the results are no more satis- 
factory. The water of crystallization was determined by heating the barium salt to 
105 C. 

Lenoir, Ann. Chem. u. Pharm., 62, 253, (1847). 

Barium pentathionate was prepared by treating Wackenroder's solution with barium 
carbonate, the salt being precipitated by the addition of alcohol. On analysis the salt 
was found to have practically the composition, BaSsOe^HaO. 

The water of crystallization was determined by combustion with lead chromate; 
at the same time carbon dioxide was determined and the carbon corresponded to 2.93% 
alcohol which was present in the salt. 

Ludwig, Archil), der Pharm., 51, 259, (1847). 

Potassium tetrathionate was prepared from Wackenroder's solution by half neu- 
tralizing with potassium carbonate. Barium and lead salts were prepared in a similar 
way. 

Kessler, Jour.f. prak. Chem., 47, 35, (1849). 

Pogg. Ann. Phys. Chem., 74, 255, (1849). 

Barium tetrathionate was prepared by using equivalent amounts of solutions barium 
acetate and tetrathionic acid and then adding alcohol. The crystals were tabular. 
The analysis of the salt was not given. 



25 

Sobrero and Selmi, Ann. chim. phys., (3) 28, 210, (1850). 

Barium tetrathionate was prepared from Wackenroder's solution by the addition 
of barium carbonate. On analysis the results obtained for baryte, sulphur, oxygen 
combined with sulphur and water agree very favorably with those of Fordos and Gelis 

(loc. cit.}. 

Spring, Ann. Chem. Pharm., 199, 97, (1879). 

The potassium and barium teirathionates were prepared from Wackenroder's 
solution by neutralizing with the carbonates and then adding alcohol. The salts showed 
on analysis, K:S = 2:4 and Ba:S = 1:4. 

Pfeiffer, Arch. Pharm., 14, 334, (1879). 

Potassium tetrathionate was prepared from Wackenroder's solution which had 
been brought to a specific gravity of 1.30 by evaporation on a water bath. This acid 
was dissolved in a mixture of ether-amyl alcohol and absolute alcohol and a dilute 
solution of potassium carbonate added. The barium salt was prepared in a similar 
way except it was precipitated from alcohol. 

The salts were analyzed in two ways. 

(a) By oxidation with bromine in hydrochloric acid solution and precipitation 
with barium chloride. 

(b) By heating and determining the sulphates. 

He concluded from his results that pentathionic acid does not exist free nor in the 
form of salts. 

Smith and Takamatsu, Jour. Chem. Soc. 37, 592, (1880). 

Barium tetrathionate was prepared from Wackenroder's solution by neutralizing 
with barium carbonate and precipitating with alcohol. The salt on analysis proved 
to be BaSiOe.l H 2 O. They further state, "We have proved to our own satisfaction 
that the attempt to neutralize pentathionic acid with alkaline earth carbonates simply 
results in the formation of tetrathionates with the separation of sulphur." 

Lewes, Jour. Chem. Soc. 39, 68, (1881). 

The pentathionates and tetrathionates of potassium and barium were prepared. 

Wackenroder's solution was concentrated to the separation of sulphur and filtered. 
The acidity was then determined by titration with standard potassium hydroxide, 
then a weak solution of barium hydroxide sufficient to half neutralize the acid was added ; 
the next day it was filtered to remove the sulphur and barium sulphate which formed. 
The filtrate was then placed over sulphuric acid in a vacuum and left to crystallize. 
After standing a few days some sulphur separated and the solution was again refiltered 
and replaced in the vacuum over sulphuric acid. At the end of eighteen days it de- 
posited a crop of fine needle shaped crystals together with a small quantity of sulphur. 
Three crops of crystals were obtained, and each crop was then dissolved in a small amount 
of water and recrystallized a second time. The first crop showed on analysis to be 
BaS 4 O 6 .3H 2 O; the second seemed to be a mixture of the pentathionate and the tetra- 
thionate; the third seemed to have the composition 



26 

The methods he used in the analysis were, 

(a) Oxidation with nitric acid, removal of all traces of acid, filtering and weighing 
the barium sulphate. The rest of the sulphur being oxidized to sulphuric acid was 
precipitated as barium sulphate. 

(&) Oxidation with chlorine in potassium hydroxide solution. 

(c} Boiling the solution with mercuric cyanide and estimation of sulphuric acid, 
mercuric sulphide and free sulphur, according to the equation of Kessler, (loc. cit.}. 

(d) Evaporation of solution to dryness with potassium hydroxide and fuse with 
potassium hydroxide and potassium nitrate, precipitating as barium sulphate. 

The water of crystallization was determined by combustion with lead chromate. 

Spring, Ann. Chem., 213, 329, (1882). 

The potassium and barium salts were prepared from Wackenroder's solution by 
neutralizing with carbonates and precipitating with alcohol. He also treated potas- 
sium thiosulphate with sulphur monochloride and obtained a salt which showed on 
analysis K:S 2:4.02. 

He has compiled a list of the results of the different investigators who have pre- 
pared potassium pentathionate from Wackenroder's solution. The ratio of potassium 
to sulphur varies from 2:3.305 to 2:5.23, the average being 2:4.506. 

Spring held that what is called pentathionic acid is nothing but sulphur dissolved 
in tetrathionic acid. 
Smith and Takamatsu, Jour. Chem. Soc., 41, 162, (1882). 

Potassium and barium salts were prepared in a similar way to that already used 
in their previous article (loc. cit.}. 

Curtius and Henkel, Jour. j. prak. Chem., N. F. 37, 142, (1888). 

Barium tetrathionate was prepared from Wackenroder's solution and barium 
carbonate. 

The Wackenroder's solution was filtered and placed in a large flask and barium 
carbonate added a little at a time until an excess had been added. It was kept in the 
flask for several hours during which time it was thoroughly shaken; the solution was 
then filtered, the filtrate being clear and did not react with litmus. A portion of the 
filtrate was analyzed and the ratio of Ba to S was found to be 1:4. 

The salt was obtained by filtering any excess barium carbonate and adding alcohol. 
The barium tetrathionate thus obtained was dissolved in a small amount of water and 
reprecipitated by alcohol. The salt obtained from the second precipitation was an- 
alyzed and found to have the composition BaS4Oe.2H 2 O. 

The Analysis: a known amount of the salt was dissolved in water and then oxi- 
dized with chlorine in potassium hydroxide solution. The solution was then filtered 
and the barium sulphate weighed. The sulphuric acid formed during the oxidation 
was precipitated by the addition of barium chloride and weighed as barium sulphate. 

The water of crystallization was determined by combustion with lead chromate. 

Hertlein, Zeitschr. f. phys. Chem., 19, 287, (1896). 

Potassium Tetrathionate: To a completely saturated solution of potassium thio- 



27 

sulphate at room temperature, so arranged as to be cooled and constantly stirred, was 
a water solution of iodine in potassium iodide added dropwise, and after each addition 
of iodine waited until it had been decolorized. The crystallized potassium tetrathionate 
was filtered off from time to time to avoid the action of iodine on the tetrathionate. 

Barium Tetrathionate: It was prepared by making a paste with barium thio- 
sulphate and water and adding solid iodine in small amounts at a time until a distinct 
brown color remained. The salt was then washed with strong alcohol and the excess 
of iodine and iodide removed, dissolved in water and a small amount of alcohol added 
which precipitated a small amount of barium tetrathionate and which was of particular 
aid in removing the finely divided sulphur and barium sulphate. The solution was 
then filtered and the rest of the barium tetrathionate precipitated by the further addi- 
tion of alcohol. 

The concentrated solutions of the barium salt decompose slightly and on this ac- 
count it was impossible to get it perfectly clear. The salt dissolves with residue but 
the solutions are always more or less opalescent; solutions of moderate concentration 
do not show this. 

PREPARATION 

I. Previous Methods Used. 

Barium tetrathionate was first prepared by Fordos and Gelis (loc. cit.). 
Since that time many investigators have prepared the salt, their methods 
being as follows: 

(1) By action of iodine on barium thiosulphate. Fordos and Gelis 
(loc. cit.)', Hertlein (loc. cit). 

(2) From Wackenroder's solution. 

(a) By half neutralizing with potassium carbonate. Ludwig 
(loc. cit.}. 

(b) By half neutralizing with barium hydroxide. Lewes (loc. cit.). 

(c) By complete neutralization with barium carbonate. Sobrero 
and Selmi (loc. cit.) ; Spring (loc. cit.) ; Pfeiffer (loc. cit.) ; Smith and Taka- 
matsu (loc. cit.)', Curtius and Henkel (loc. cit.). 

(3) By action of barium acetate on tetrathionic acid. Kessler (loc. 
cit.). 

II. General Procedure of Method Used. 

25 grams of BaSgOa.lH^O and 12.5 grams of resublimed iodine were 
finely pulverized in separate mortars. Then from 80 to 100 cc. of alcohol 
of definite density were added to the mortar containing the barium thio- 
sulphate and the iodine added a little at a time thoroughly mixing after 
each addition, until all the iodine had been added and there remained a 
slight excess of iodine. 



28 

The mixture was left in the mortar from two to three hours stirring 
occasionally, transferred to a Biichner using alcohol as the wash liquid 
and washed free of iodine and iodide by means of alcohol. 

The residue was dissolved in the smallest possible amount of water at 
a temperature not above 20, filtered through a specially prepared Gooch 
and the barium tetrathionate precipitated from the filtrate by the addition 
of alcohol, absolute alcohol, absolute alcohol-ether (1:1), or acetone either 
by allowing to stand over night or by cooling, the results being shown in 
A, C, and D of Table VII. In B of Table VII is shown the result obtained 
by cooling the water solution of barium tetrathionate. 

III. Preparation of Barium Thiosulphate. 

The barium thiosulphate was prepared by mixing solutions containing 
equivalent amounts of sodium thiosulphate and barium chloride. 

463.9 grams of C. P. hydrous sodium thiosulphate were dissolved in 550 
cc. of water, and 456.6 grams of C. P. hydrous barium chloride were dis- 
solved in 1500 cc. of water, both solutions being filtered before used. 

The solution of sodium thiosulphate was heated nearly to boiling and 
kept hot while the barium chloride solution was added from a burette 
at the rate of two or three drops per second, stirring constantly. 

After all the barium chloride had been added, the barium thiosulphate 
was washed by decantation six or eight times, then placed on a Buchner 
and washed, using suction until free of chlorides. 

IV. Difficulties Encountered. 

In the first experiments in which barium tetrathionate was prepared 
several difficulties were encountered and the yields were very low. 

(1) Barium thiosulphate does not form paste. 

The barium thiosulphate did not form a paste with water as did the 
sodium thiosulphate and for this reason the condition for complete re- 
action was not so good. 

(2) Reaction incomplete. 

When alcohol alone was added to the barium thiosulphate and the iodine 
added a little at a time, the reaction would not go to completion and a 
large residue of barium thiosulphate remained. These results are shown 
in Table VII, trials 1 to 8 inclusive. This difficulty was probably of a 
mechanical nature due to a protective coating of barium tetrathionate 
formed around the particles of barium thiosulphate thus preventing the 
contact with the iodine in solution. When water was added to the alcohol 



29 

which was added to the barium thiosulphate before the addition of the 
iodine, the reaction would go to completion. The addition of water to 
the alcohol either increased the solubility of the barium tetrathionate 
and thus removed the protective coating, or permitted the barium tetra- 
thionate to be formed in a more granular form and the protective coating 
did not form; in either case the reaction would go to completion. 

(3) Determination of density of alcohol used. 

Since it was shown that water must be added to the alcohol which 
was added to the barium thiosulphate before the addition of iodine, it 
was necessary to determine the density of alcohol used which would permit 
the reaction to go to completion and still not have the water content high 
enough to dissolve any considerable amounts of barium tetrathionate. 
This was done by increasing the density of the alcohol used until there 
was no residue of barium thiosulphate. 

(4) The condition of the barium tetrathionate formed. 

The barium tetrathionate, obtained when undiluted alcohol was added 
to the barium thiosulphate before the addition of iodine, was gummy and 
difficult to filter; while the barium tetrathionate, obtained when diluted 
alcohol was used, was crystalline and easily filtered. 

TABLE VII 

A. Precipitated by allowing to stand over night. Alcohol specific gravity 
0.817 at 20, added to the barium thiosulphate. 



Cc. of water 
Cc. of alcohol used to dis- 
added to barium solve barium 
Trial, thiosulphate tetrathionate. 

1 350 14 


Precipitated 
from. 

alcohol = 


Cc. 

used. 

60 


Yield 
in %. 
8 


2 


3 cc. water 20 cc. 


14 


ab. alcohol = 


60 


21.5 




alcohol 










3 


20 


35 


ab. alcohol = 


100 


12.1 


4 


40 


26 


ab. alcohol = 


100 


10.7 


5 


35 


20 


ab. alcohol = 


200 


13.7 


6 


50 


20 


ab. ale. -ether = 


200 


26.9 


7 


50 


20 


acetone = 


170 


10.2 



Precipitated by cooling a water solution. Alcohol specific gravity 0.817 
at 20 added to the barium thiosulphate. 

8 50 23 water = 23 9.1 

Precipitated from an absolute alcohol-ether solution (1:1) by cooling. 
Alcohol specific gravity 0.887 at 20 added to barium thiosulphate. 

9 85 25 abs. alc.-ether = 200 40.3 



30 



D. Precipitated by allowing to stand over night. Alcohol specific gravity 
0.887 at 20 added to barium thiosulphate. 

10 90 35 abs. alc.-ether = 250 59. 

11 90 36 abs. alc.-ether = 400 70. 

12 110 27 abs. alc.-ether = 400 65. 

13 100 30 abs. alc.-ether = 500 70 . 

% 
The results of the above experiments show that the highest yields were 

obtained when absolute alcohol-ether was added to the nitrate and allowed 
to stand over night. The low results in the first eight trials was largely 
due to the fact that the reaction between the iodine and barium thiosul- 
phate did not go to completion. 

COMPARATIVE ANALYSIS FOR PURITY 

I. By Heating the Barium Tetrathionate. 

In order to get an idea of the purity of the barium tetrathionate a series 
of experiments were made, the results of which are shown in Tables VIII 
and IX. 

TABLE VIII 

A. Barium tetrathionate prepared by the method of Fordos and Gelis 
modified, dissolved in water and precipitated by the addition of 
absolute alcohol-ether (1:1). 



Trial. 

1 

2 

3 

4 

5 

6 

7 

8 

9 
10 
11 
12 
13 
14 



Barium tetia- 


Barium sulphate 


Barium sulphate 


Error in 


thionate used. 


calculated. 


found. 


barium sulphate. 


Gm. 


Gm. 


Gm. 


Gm. 


0.5025 


0.2950 


0.2968 


+0.0018 


0.5048 


0.2963 


0.2979 


+0.0016 


0.5002 


0.2936 


0.2948 


+0.0013 


0.5031 


0.2953 


0.2981 


+0.0028 


0.4955 


0.2908 


0.2887 


-0.0021 


0.5060 


0.2970 


. 2954 


-0.0016 


0.5047 


0.2952 


0.2943 


-0.0019 


0.5020 


0.2947 


0.2923 


-0.0024 


0.5099 


0.2993 


. 2994 


+0.0001 


0.4983 


0.2925 


. 2927 


+0.0002 


0.5180 


0.3041 


0.3055 


+0.0014 


0.5046 


0.2962 


0.3008 


+0.0046 


. 5023 


0.2949 


0.2974 


+0.0025 


0.5007 


0.2939 


0.2961 


+0.0022 



B. 



15 
16 



Barium tetrathionate prepared by the method of Fordos and Gelis 

modified, dissolved in water and cooled. 

0.5139 0.3017 0.3014 -0.0003 

0.5014 0.2943 0.2942 -0.0001 



31 

In Table VIII are shown results obtained by heating the barium tetra- 
thionate. 

About one half gram of the hydrous barium tetrathionate was weighed out 
into a crucible and heated with a very low Bunsen flame for about one- 
half hour, keeping the lid loosely fitted on the crucible, then gradually 
raising the temperature to the full heat of the Bunsen for ten minutes, 
placed in a desiccator, cooled and weighed. In some cases a few drops 
of concentrated sulphuric acid were added to the barium sulphate and 
then carefully driven off by heating; this made no change in the results. 

In calculating the barium sulphate from the hydrous barium tetrathio- 
nate, the composition of the hydrous barium tetrathionate was assumed to 
be BaS4O 6 .2H 2 O, and the products formed when heated to be barium 
sulphate, sulphur dioxide and sulphur. 

II. By Oxidation of Barium Tetrathionate and Precipitating with Barium 

Chloride Solution 

The results shown in Table IX were obtained by weighing out given 
amounts of hydrous barium tetrathionate, dissolving in water, oxidizing 
with bromine water and afterwards boiling off the excess, and precipitating 
the sulphate ion by the addition of a barium chloride solution observing 
all the precautions given under Table II. 

The hydrous barium tetrathionate was obtained by addition of an abso- 
lute alcohol -ether (1:1) solution to a freshly filtered concentrated water 
solution of barium tetrathionate and allowing to stand over night. 

TABLE IX 

Barium tetrathionate Barium sulphate Barium sulphate Error in barium 

taken. calculated. found. sulphate. 

Gm. Cm. Gm. Gm. 

1.0000 2.3480 2.2976 -0.0514 

0.5000 1.1740 1.1604 -0.0136 

0.5000 1.1740 1.1587 -0.0153 

The results shown in Table VIII, trials 1 to 4 inclusive were obtained 
from two different samples, but the samples were analyzed about three 
weeks after they were prepared; the results in trials 5 to 8 inclusive were 
obtained from two other different samples analyzed two days after their 
preparation ; the results in trials 9 to 14 were from three entirely different 
samples analyzed two days after their preparation. 

The results in B, Table VIII, were obtained from a sample precipitated 



32 

from a water solution, carefully dried between niters and immediately 
analyzed. 

It might also be stated that the results obtained in trials 9 to 14 inclu- 
sive were from samples prepared during the hot summer months. 

The results of both Tables VIII and IX show the hydrous barium tetra- 
thionate to be quite pure, but it slowly decomposes particularly above 
20. 

WATER OF CRYSTALLIZATION 

Fordes and Gelis (loc. cit.) obtained the salt from a water solution and 
found that each molecule of the salt contained two molecules of water of 
crystallization, the result being obtained by difference. Sobrero and 
Selmi (loc. cit.) obtained results in agreement with those of Fordos and 
Gelis. Lewes (loc. cit.) obtained two salts of hydrous barium tetrathionate, 
one of which contained one and the other three molecules of water of crystal- 
lization. The results were obtained by combustion with lead chromate. 
Curtius and Henkel (loc. cit.) determined the water of crystallization by 
combustion with lead chromate and found it to contain two molecules 
of water of crystallization. Hertlein (loc. cit.) prepared barium tetra- 
thionate according to the method of Fordos and Gelis, precipitated by 
means of alcohol and dried the salt over sulphuric acid and found that it 
contained one molecule of water of crystallization. He does not state 
the results of his analysis nor does he state what method he used. 

BEHAVIOR OF THE HYDROUS SALT WHEN EXPOSED TO AIR; TO AIR OVER 
CONCENTRATED SULPHURIC ACID AND TO AIR SATURATED WITH 

MOISTURE 

In order to determine the behavior of hydrous barium tetrathionate 
when exposed to air, air over concentrated sulphuric acid, and air saturated 
with moisture, a series of experiments were carried out, the results of which 
are shown in Table X. 

The hydrous barium tetrathionate was spread out on one of two tared 
watch glasses. In A, the watch glasses were exposed to air; in B, to air 
over concentrated sulphuric acid in a desiccator; in C, to air over water 
in a desiccator. 

The results of Table X seem to show that hydrous barium tetrathionate 
is slightly deliquescent when exposed to air. Further, that when exposed 



33 

to air over concentrated sulphuric acid it slowly loses some of its water 
of crystallization. 

TABLE X 

A. Hydrous barium tetrathionate exposed to air. 

Weight of hydrous 

barium tetrathionate. Time exposed. Loss in weight. Gain in weight. 

Gm. Days. Gm. Gm. 

1.0058 0.0000 

1.0058 2 0.0000 

1.0075 10 0.0017 

B. Hydrous barium tetrathionate exposed to air over concentrated 
sulphuric acid. 

1.0075 0.0000 

1.0040 2 0.0035 

0.9977 8 0.0098 

0.9927 14 0.0148 

0.9918 20 0.0157 

C. Exposed to saturated air. 

1.0052 0.0000 

1.2905 2 0.2853 

SUGGESTED METHOD FOR PREPARATION 

Weigh out 50 grams of BaS2Os.lH2O and 25 grams of iodine, placing 
each in separate mortars and pulverize them very fine. To the barium 
thiosulphate in the mortar add 100 cc. of alcohol specific gravity approxi- 
mately 0.887 at 20 and thoroughly mix. Then add the iodine a little 
at a time, mixing thoroughly after each addition, until all the iodine has 
been added and there remains a slight excess of iodine. The addition and 
mixing should require about three quarters of an hour. Allow the mixture 
to remain in the mortar a short time after all the iodine has been added 
and filter through a Buchner using suction. 

Wash the precipitate free of iodine and iodide by use of alcohol. The 
absence of iodine may be told by the color of the wash alcohol ; the absence 
of iodide by the addition of a few drops of a dilute solution of lead acetate. 

After these impurities have been removed, the precipitate is dried as 
much as possible by pressing between filter paper to remove most of the 
alcohol. This nearly dry precipitate is then dissolved in the least possible 
amount of water (about 65 cc.) at not above 20. This solution is then 
filtered using suction through a specially prepared Gooch, which consists 
of two separate layers of barium sulphate and flowers of sulphur with a 



34 

layer of asbestos on the top and bottom and also between each of the 
four layers. This solution is best filtered into a test tube placed within 
an Erlenmeyer filtering flask. To the filtrate add several drops of iodine 
dissolved in alcohol to a slight iodine coloration. This filtrate, which 
usually has a slight turbidity, is added to 700 cc. of absolute alcohol- 
ether (1:1) in a crystallizing dish, placed in an empty vacuum desiccator 
and the air removed and allowed to stand from twelve to twenty-four 
hours. If the weather is cold the yield is increased by placing out of doors. 
The yield is 60% to 75% of the theoretical. 

Recrystallization from a water solution. 

Hydrous barium tetrathionate may also be obtained by cooling the 
water solution by means of a mixture of salt and ice. The rate of crystal- 
lization is extremely slow and the yield not very satisfactory. 

QUALITATIVE DECOMPOSITION 

The salts of the tetrathionate decompose into a sulphate, sulphur dioxide, 
and sulphur when heated. In order to get an idea of the decomposition 
of tetrathionates in a boiling solution, a series of qualitative experiments 
were made. 

About 1 gram of hydrous barium tetrathionate was dissolved in 100 cc. 
of water and transferred to an Erlenmeyer flask which was attached to 
a Liebig condenser. The solution was heated and became decidedly 
turbid as soon as it began to boil. 

The odor of sulphur dioxide was plainly noticeable at the mouth of the 
condenser, and when the evolved gas was led into a dilute solution of 
potassium permanganate it was readily bleached. 

The residue consisted of barium sulphate and sulphur with a slight 
trace of sulphite and thiosulphate. 

The solution was boiled for 30 hours and when tested with mercurous 
nitrate solution gave a yellow precipitate indicating the presence of tetra- 
thionate or pentathionate or both, or possibly higher thionates, but the 
absence of any appreciable amounts of trithionate, sulphite, or thiosul- 
phate. Further, tests were made to determine if any hydrogen sulphide 
were formed during the decomposition. 

(I) Filter paper moistened with lead acetate solution was held at the 
mouth of the condenser and negative results obtained. 

(II) Several drops of lead acetate solution were added to the solution 



35 

of barium tetrathionate and the solution boiled with a reflux for one 
hour before any darkening was noticeable. At the end of two hours the 
solution began to turn black, and at the end of six hours it was black. 

The results of the above qualitative tests show that the barium tetra- 
thionate solution when boiled decomposes into barium sulphate, sulphur 
dioxide, and sulphur. 

QUANTITATIVE DECOMPOSITION 

(I) Preliminary. 

Before making the quantitative determinations some preliminary experi- 
ments were made to get some idea of the time required for the decomposi- 
tion. 

1. 1 gram of hydrous barium tetrathionate was dissolved in water and 
placed in a flask attached to a reflux condenser and boiled 8.5 hours. 
The solution was filtered and again boiled 2 hours. The weight of barium 
sulphate obtained by the second boiling was .0143 grams. 

2. 1 gram of hydrous barium tetrathionate was treated exactly as in 
1 except it was boiled the first time for 8 hours. The solution was filtered 
and again boiled for 5.5 hours. The weight of barium sulphate obtained 
by the second boiling was .0179 grams. 

3. 1 gram of hydrous barium tetrathionate was treated as in 1 except 
it was boiled for 7.5 hours. The weight of barium sulphate obtained was 
.4160 grams as compared to .5870 grams, the theoretical yield. 

(II) Description of the Apparatus. 

After considerable experimenting the set-up shown in Fig. 2 was chosen, 
although in carrying out the experiments two absorption tubes in series 
were used. 

The carbon dioxide was generated by a Kipp not shown and then passed 
through a solution of sodium carbonate contained in A to the decomposi- 
tion flask C, the inlet tube extending below the surface of the solution. 
The decomposition flask C was attached to a reflux condenser B in order 
to prevent loss by boiling and thus keep the volume of the solution constant. 
Connected to the reflux condenser B was a ten bulbed Meyer absorption 
tube D which contained the bromine water or alkaline hypobromite to 
oxidize the evolved sulphur dioxide. E was filled with some of the same 
solution as was used in the absorption tube. 



36 

The type of absorption tube used was the same as used by Lunge, Jour. 
Soc. Chem. Ind., 9, 1013 (1890). 

(Ill) Procedure. 

The apparatus was first tested to be sure there were no leaks. After 
the set-up was found to be gas tight, 1.0000 gram of hydrous barium tetra- 
thionate was dissolved in water and transferred quantitatively to the 
decomposition flask C so there were 100 cc. of solution in the flask. The 
air in the system was then driven out by the carbon dioxide and the solu- 




Fig. 2. Decomposition and Absorption Apparatus. 

tion heated. After the boiling had started the carbon dioxide was con- 
tinued at the rate of about two bubbles per second during the entire time 
of the boiling. When the boiling was discontinued, the system was swept 
out by carbon dioxide for one half hour. 

The analysis shown in Table XI consists of three parts. 

(1) Determination of barium sulphate obtained from the direct de- 
composition of the barium tetrathionate during the boiling. 



37 

The contents of the decomposition flask was transferred quantitatively 
to a beaker, together with the small amount of sulphur which collected 
in the lower part of the condenser. The solution was then filtered through 
a hard filter and the filter thoroughly washed with water. The residue 
on the filter, which consisted of barium sulphate and sulphur, was washed 
into a beaker and liquid bromine added, the solution being kept warm 
for three hours. The decomposition flask was also treated with hot bro- 
mine water to remove any adhering particles of sulphur, and this solution 
added to that containing the barium sulphate and sulphur. 

The free sulphur was oxidized to sulphuric acid, while the barium sul- 
phate remained unchanged. 

The solution was then boiled to remove the bromine and filtered through 
a weighed Gooch, the increase in weight being the barium sulphate formed 
from the direct decomposition of the barium tetrathionate. 

(2) Determination of barium sulphate obtained from the sulphur formed 
during the boiling. 

The filtrate obtained from (1) should contain all the sulphur formed 
during the decomposition by boiling as sulphuric acid. The sulphate 
ion was precipitated by the addition of a solution of barium chloride, 
the barium sulphate being that obtained from the oxidation of the sulphur. 

(3) Determination of barium sulphate obtained from the sulphur 
dioxide formed during the boiling. 

When bromine was used in the absorption tubes as in trials 1 to 12 
inclusive, the contents of the tubes was transferred quantitatively to a 
beaker, the excess bromine boiled off, and precipitated by the addition 
of a solution of barium chloride. 

When alkaline hypobromite was used in the absorption tubes as in 
trials 13, 14 and 15 the contents of the tubes was transferred quantita- 
tively to a beaker, made slightly acid with hydrochloric acid and care- 
fully evaporated to dry ness, the last stages being on a water bath. The 
beaker containing the residue was then heated in an air oven at 120 
for two hours, cooled, and the residue dissolved in water and the solution 
filtered to remove the silica. The sulphate ion was then precipitated by 
the addition of a solution of barium chloride, the barium sulphate being 
that obtained from the oxidation of the sulphur dioxide. 
(IV) Purification of Bromine. 

Since practically all bromine contains small amounts of sulphuric acid 



38 

and bromine -was to be used to oxidize the sulphur dioxide evolved, it was 
necessary to remove the sulphate from the bromine before using it. 

500 grams of ordinary N. F. bromine was washed five times with water 
in a separatory funnel; then 10 grams of barium hydroxide were dissolved 
in water and added to the bromine in a separatory funnel and shaken for 
two hours; the bromine was then washed twice with water and poured 
into a long necked distilling flask containing 50 cc. of water. 

The top of the distilling flask was closed with a glass stopper packed with 
asbestos, and the side arm extended into a Liebig condenser through an 
asbestos plug, the bromine being collected in a flask surrounded with ice 
water. The first part of the distillate and a small amount of bromine re- 
maining in the distilling flask at the end of the operation were discarded. 

The distilling flask was immersed in a water bath kept at a temperature 
slightly above the boiling point of bromine, and fine capillary tubes sealed 
near the lower ends were placed within the flask which permited the bro- 
mine to distil without bumping. 

The bromine prepared according to the above method was tested for 
presence of sulphates according to Krauch-Merck, 76, and showed no 
cloudiness within twelve hours. 

(V) Preparation of Sodium Hypobromite. 

The sodium hypobromite was always freshly prepared before using. 
30 grams of sodium hydroxide purified by alcohol were dissolved in 200 
cc. of water and 5 cc. of the purified bromine added slowly from a pipette. 

About 100 cc. were placed in each of the absorption tubes. 

(VI) Blank Experiment. 

Since all sodium hydroxide contains traces of sulphur, it was necessary 
to determine how much barium sulphate was obtained from the sodium 
hydroxide alone which was used to make the sodium hypobromite. 

30 grams of sodium hydroxide purified by alcohol were dissolved in 
water and bromine added. The solution was then neutralized with 
hydrochloric acid and carefully evaporated to dryness, the last stage of 
which was done on a water bath, and then heated in an air oven for two 
hours at 120. 

The residue in the beaker after cooling was dissolved in water and 
the solution filtered to remove any silica. The filtrate was then heated 
to boiling and a solution of barium chloride added. 



39 

The average of three trials was 20 mg. of barium sulphate and this 
correction has been applied in Trials 6, 7, and 8 in Table XII. 
(VII) Results in Table XL 

In trials 1 to 12 inclusive bromine water was used to oxidize the sulphur 
dioxide, while in trials 13 to 15 inclusive alkaline hypobromite was used. 

In trials 1 to 10 inclusive, elliptical bulbed absorption tubes were used, 
while in trials 11 to 15 inclusive, spherical bulbed absorption tubes were 
used. 

The barium sulphate representing the sulphur dioxide was always low. 

In order to see if any of the sulphur dioxide was going through the 
absorption tubes unoxidized, two changes were made: 

(1) Spherical bulbed absorption tubes were substituted for the ellip- 
tical bulbed ones in order to increase the time of the gas through the 
oxidizing solution. 

(2) The alkaline hypobromite was substituted for the bromine water, 
for, if any of the sulphur dioxide were converted to sulphur trioxide by 

TABLE XI 
A. Bromine water used" in elliptical bulbed absorption tubes. 



Time of 
boiling. 
Trial. Hrs. 


Barium 
tetra- 
thion- 
ate 
used. 
Gm. 


BaSO4 
from 
direct de- BaSO4 from 
composition oxidation 
of Ba tet. of SO2. 
Gm. Gm. 


BaS0 4 
from ox- 
idation 
of S. 
Gm. 


Ratios found 
to a BaSO* basis. 
BaS04:S0 2 :S. 


1 


4 




1.0000 


0.2812 


0. 


2040 





3239 


1 


.727: 


1.15 


2 


6 


5 


1.0000 


0.3258 





2715 





4105 


1 


.832: 


1.26 


3 


7 


75 


1.0000 


0.4113 





3065 





5211 


1 


.742: 


1.26 


4 


8 


3 


1.0000 


0.4734 





4548 





6573 


1 


.960: 


1.39 


5 


8 




1.0000 


0.4676 





3916 





6311 


1 


.837: 


1.349 


6 


8 




1 . 0000 


0.4146 





3290 





5850 





.796: 


1.418 


7 


7 




. 5000 


0.1435 





1208 





1297 


1 


.840: 


.903 


8 


9 




1.0000 


0.3350 





2614 





3422 


1 


.783: 


1 S 028 


9 


9 




1.0000 


0.3700 





2746 





4378 


1 


.746: 


1.189 


10 


7 


75 


1.0000 


0.3500 





2685 


o 


3748 


1 


.767: 


1.067 


B. 


Bromine 


water used in spherical 


bulbed absorption 


tubes. 




11 


7 


75 


1.0000 


0.3347 





2559 





3750 


1:.765: 


1.118 


12 


8 


75 


1.0000 


0.3536 





2692 





4095 


1:.761: 


1.157 


C. 


Alkaline 


hypobromite used 


in spherical 


bulbed absorption tubes. 


13 


7 


75 


1.0000 


0.3569 





3355 





4171 


1:.940: 


1.168 


14 ' 


7 




1.0000 


0.5111 





3518 





7496 


1:.688: 


1.464 


15 


7 


5 


1.0000 


0.4160 


0.3136 





5261 


1-..754: 


1.265 



40 

the catalytic action of the carbon dioxide (Bigelow, Zeitschr. phys. Chem., 
26, 531 (1898)); (Tithoff, Zeitschr. phys. Chem., 45, 679 (1903)) the sulphur 
trioxide would be retained by the excess of sodium hydroxide. Further, 
the excess of sodium hydroxide reacts with the carbon dioxide reducing 
the size of the bubbles of gas and thus increases the efficiency of oxidation. 

The results of Table XI do not show that the barium tetrathionate 
solution decomposes according to the equation 

BaS 4 6 = BaS0 4 + SO 2 + 2S 

The barium sulphate was chosen as the basis to obtain the ratios given 
since it was the least variable. 

For example, the ratios of Trial 15 were obtained as shown below, while 
all the others were obtained in a similar way. 

.4160 ^ 233.44 = .001781 1.781 + 1.781 = 1 BaSO 4 

.0861 -^ 64.07 = .001344 1.344 -;- 1.781 = .754 SO 2 

.0723 -T- 32.07 = .002253 2.253 -f- 1.781 = 1.265 S 

QUANTITATIVE DECOMPOSITION INCLUDING THE ANALYSIS OF THE 

FILTRATE 

As already stated, the results given in Table XI do not show that barium 
tetrathionate decomposes from a boiling solution according to the equa- 
tion given above. 

Since the amounts of sulphur dioxide and sulphur were always low and 
somewhat variable, it seemed possible that the above reaction takes place 
and that the sulphur dioxide and the sulphur react with the thionate in 
the solution. In order to show this, it was necessary to analyze the nitrate 
obtained after filtering off the barium sulphate and sulphur which were ob- 
tained by boiling the barium tetrathionate solution. 

The filtrate was analyzed by the addition of liquid bromine to the solu- 
tion and keeping the solution warm for three hours. All the barium was 
precipitated as barium sulphate, and all the remaining sulphur was oxi- 
dized to sulphuric acid. The excess of bromine was removed by boiling 
the barium sulphate filtered off and weighed, and the sulphate ion pre- 
cipitated by the addition of a solution of barium chloride. 

The headings used in Table XII are as follows: 

"BaSCU From Decomposition of Barium Tetrathionate" means the 
total barium sulphate obtained by boiling the barium tetrathionate, and 
includes the barium sulphate obtained by the direct decomposition, the 



41 

barium sulphate from the sulphur dioxide, and the barium sulphate from 
the sulphur. 

"BaSO 4 From Filtrate" is divided into two parts, for when oxidized 
with the bromine, barium sulphates separated out directly and all the 
remaining sulphur was oxidized to sulphuric acid. 

"BaSO 4 Found From Same Amount of Barium Tetrathionate" means 
that the same weight of hydrous barium tetrathionate was taken as that 
used in the decomposition flask, dissolved in water in a beaker and oxi- 
dized with bromine. The total weight of barium sulphate obtained in 
this way was always slightly less than the theoretical calculated from the 
weight of hydrous barium tetrathionate taken. 

Trial 1, Table XII, was the same decomposition as Trial 8 in Table XI; 
Trial 2 in Table XII the same as Trial 9 in Table XI and etc. 

TABLE XII 
A. Bromine water used in elliptical bulbed absorption tubes. 

BaSO4 from filtrate Total amt. 



Trial. 
1 


Barium 
tetra 
thionate 
used. 
Gm. 

1.0000 


BaS0 4 BaS0 4 BaSO 4 of BaSO< 
from from from Total found rom 
decomposi- direct all re- BaSOi same famt. Error 
tion of decompo- maining found of Ba. in 
Ba. Tet. sition. sulphur. in Tet. BaSOi. 
Gm. Gm. Gm. analyses. Gm. Gm. 

0.9386 0.2326 1.0500 2.2206 2.2976 -0.0770 


2 


1 . 0000 


1.0824 0.1972 0.9605 2.2401 2.2976 


-0.0575 


3 


1.0000 


0.9933 0.2276 1.0233 2.2447 2.2976 


-0.0529 


B. Bromine water used in spherical bulbed absorption tubes. 


4 


1.0000 


0.9656 0.2383 1.0442 2.2431 2.2976 


-0.0495 


5 


.1.0000 


1.0323 0.2279 1.0070 2.2672 2.2976 


-0.0304 


C. Alkaline hypobromite used in spherical bulbed absorption 


tubes. 


6 


1 . 0000 


1.1095 0.2215 1.0185 2.3495 2.2976 


+0.0519 


7 


1 . 0000 


1.6135 00743 0.6722 2.3595 2.3208 


+0.0387 


8 


1.0000 


1.2557 0.1668 0.8714 2.2939 2.3208 


-0.0269 



The results in Table XII show that the loss in sulphur dioxide and sul- 
phur in the boiling solution was recovered in the filtrate, thus proving that 
secondary reactions occur in the solution during the boiling. 

Suppose the results of Trial 5 in Table XII be taken (These results 
were from the filtrate in Trial 12 in Table XI). 

As previously stated, when the filtrate was oxidized by liquid bromine 
all the barium was precipitated as barium sulphate and the remaining 
sulphur was oxidized to sulphuric acid. If the barium sulphate, which 



42 

is formed directly when the bromine was added to the nitrate, be filtered 
from the sulphuric acid and weighed, it is possible to get an idea of the 
total weight of barium sulphate that should be obtained from the nitrate. 

For example: if all the barium were present as tetrathionate, 
0.2279 X 4 = 0.9116 gm. of barium sulphate which should be found from 

the nitrate 

if all the barium were present as pentathionate, 
.2279 X 5 = 1.1395 gm. of barium sulphate which should be found from 

the nitrate. 
Whereas, 

.2279 + 1.0070 = 1.2349 gm. of barium sulphate actually found in the 

filtrate. 

From the calculations it may be seen that the weight of the barium 
sulphate actually found from the filtrate may be accounted for by the 
assumption that higher thionates than the tetrathionate were formed in 
the boiling solution. 

If the presence of the higher thionates be assumed, they are more stable 
at the boiling temperature than the tetrathionate which is certainly not 
in agreement with the generally accepted Mendeleeff (loc. cit.) structure. 

The presence of colloidal sulphur will not explain the differences found. 

CRYSTALLOGRAPHY OF SODIUM AND BARIUM TETRATHIO- 

NATES 

BIBLIOGRAPHY 

No reference was found in the chemical literature where any crystallographic study 
had been made of the sodium salt. 

Curtius, Jour.f. prak. Ckem., N. F. 24, 225, (1881). 

Barium tetrathionate was prepared by completely neutralizing Wackenroder's 
solution with barium carbonate. The solution was analyzed and the ratio of barium 
to sulphur was found to be about 1:4. 

The salt was also prepared from the solution by the addition of alcohol and crystals 
1 /2 cm. long and l l /i mm. wide were obtained. The crystals were dried in a desiccator 
over calcium chloride. 

The crystals were observed through the polarizing microscope and were found to 
be rhombic of apparently hemimorphic habits and possessed a very definite cleavage 
parallel to the macro and brachypinacoid. 

Shaw, Jour. Chem. Soc., 43, 351, (1883). 

Potassium tetrathionate and pentathionate were prepared from Wackenroder's 



43 

solution by neutralizing with potassium hydroxide, concentrating on a water bath, and 
then placed in a vacuum over sulphuric acid and fractionally crystallized. The first 
and second crops of crystals showed the ratio of potassium to sulphur to be 2:4; the 
third, fourth and fifth, 2:4.6; the sixth (selected) 2:5. 

The potassium tetrathionate crystals when examined under the microscope proved 
to be hemimorphic forms belonging to the orthorhombic system. 

Curtius and Henkel, (loc. cit.}. 

Barium tetrathionate was prepared as previously described. It had a fine silvery 
texture with well formed crystal plates. When the crystals were examined with polar- 
ized light they were found to be monoclinic in nature and almost always twinned. 

Fock and Kluss, Ber., 2428, (1890). 

Potassium tetrathionate was prepared by the gradual addition of iodine to a con- 
centrated solution of potassium thiosulphate. The separated salt was washed free of 
potassium iodide with absolute alcohol, dissolved in warm water, filtered, and the fil- 
trate treated with alcohol. The precipitate consisted of large glistening tabular crys- 
tals. 

The salt was analyzed by oxidizing a known amount in solution with bromine water, 
and precipitated with barium chloride. Also, a known amount of the salt was heated 
and the sulphate determined. These analyses show the salt to be K^Oe. 

A crystallographic study of the above crystals was made and they were found to 
be identical with those described by Rammelsberg (Krys... Phys. Chem. I, 495) and who 
gave the composition of the crystalline salt as KgSsOe. (Rammelsberg's salt was pre- 
pared from Wackenroder's solution). 

Potassium tetrathionate crystallizes in peculiar hemimorphic or hemihedral forms 
belonging to the monoclinic (monosymmetric) system, and not to the rhombic system 
as stated by Shaw (loc. cit.}. 

Potassium pentathionate was prepared according to the method of Debus (loc. 
cit. 294). The saH on analysis proved to be 2K 2 S-A>.3H 2 O. They made a crystallo- 
graphic study of this salt. 

EXPERIMENTAL 

(I) Sodium Tetrathionate. 

(1) Crystallization from Absolute Alcohol-Ether. 

The crystals were obtained by adding a saturated water solution of 
sodium tetrathionate at 50 to 00 to an absolute alcohol-ether mixture 
and allowing it to stand for twelve hours. The crystals thus obtained 
were very small and occur in aggregate. The widths of the crystal aggre- 
gates varied from .000 mm. to .03 mm., while the widths of the individual 
crystals varied from .001 mm. to .01 mm. The lengths of the aggregates 
and individual crystals were from two to four times their widths. 



44 




(2) Crystallization from Water. 

The crystals were obtained from a saturated water solution of sodium 
tetrathionate at 50 to 60 and cooling with a mixture of salt and ice for 
about two hours; they were much larger than those obtained from the 
absolute alcohol-ether solution and they did not occur in aggregates. 

The crystals obtained from the water solution varied from .06 mm. to 
.3 mm. in width, while their lengths were about two to four times as great. 

(3) Optical Characteristics of the Crystals. 

The crystals obtained from the water solution (See 
Fig. 3) were examined under the polarizing micro- 
scope and the following results obtained : probably 
monoclinic ; generally twinned, both penetration and 
contact, sometimes showing a more or less hour glass 
structure ; the crystals show on the side pinacoid the 
normal emergence of Bxo = a; the acute bisectrix c 
is almost parallel to the trace of one of the small 
faces which is inclined at an angle of about forty 
degrees from the direction of elongation; adjacent 
twins have a difference in extinction of about two to 
four degrees; a = 1.53 .005; c = 1.65 =*= .005; 
birefringence = .12 (high); 2 V is small, about ten 
to twenty degrees. The optical sign is +. The 
edges of the crystals were somewhat rounded which 

prevented accurate measurement of angles between the traces of crystal- 

lographic faces. 

(II) Barium Tetrathionate. 

(1) Crystallization from Absolute Alcohol-Ether. 

The crystals from the absolute alcohol-ether mixture were obtained 
by adding a saturated water solution of barium tetrathionate at room tem- 
perature to an absolute alcohol-ether mixture and allowing to stand for 
twelve hours. The crystals were rod or needle shaped, and the large ones 
varied in width from .003 mm. to .007 mm. and in length from .01 mm. 
to .045 mm. 

(2) Crystallization from Water. 

The crystals were obtained by cooling a saturated water solution of 
barium tetrathionate at room temperature by means of liquid air. The 



Fig. 3. Highly magni- 
fied twin crystal of 
Na 2 S4O6.2H 2 O show- 
ing emergence of 
Bxo = ft on side 
pinacoid. 



45 

dimensions of the crystals were from two to five times those obtained from 
the absolute alcohol-ether mixture. 

(3) Optical Characteristics of Crystals. 

The crystals obtained from the water solution were examined under 
the polarizing microscope and the following results obtained: rod shaped, 
probably monoclinic; inclined extinction, angle large, 30; crystals in- 
variably twinned, contact and frequently poly synthetically ; elongation 
negative; a = 1.61 == .005; c = 1.70 .005; birefringence = .09. 

ZINC TETRATHIONATE 

BIBLIOGRAPHY 

Fordos and Gelis, Ann. chim. phys., (3) 6, 492, (1842). 
Jour. /. prak. Chem., 28, 478, (1843). 

Zinc tetrathionate was prepared by mixing solutions of barium tetrathionate and 
zinc sulphate and filtering. They further state that the zinc tetrathionate may be 
obtained from the solution either by evaporation or by the addition of alcohol. 
Curtius, Jour.f. prak. Chem., N. F. 24, 237, (1881). 

A tetrathionate of zinc was prepared from Wackenroder's solution and zinc car- 
bonate. 

To Wackenroder's solution, previoulsy filtered to remove sulphur, freshly pre- 
cipitated zinc carbonate was added to neutralization. To this a volume of Wacken- 
roder's solution equal to that already used was added and the solution filtered. A 
small amount of the solution was boiled in a small tube and it decomposed explosively 
into zinc sulphate, sulphur, and sulphur dioxide. ' 

The salt was obtained from the solution by evaporating to a syrupy liquid on a 
water bath at a low temperature for several days, then placing it in a vacuum and 
further concentrating to a crystalline mass which was separated from the mother liquor 
and dried between filter papers. The formula of the salt was not stated. 
Curtius and Henkel, Jour.f. prak. Chem., N. F. 37, 147, (1888). 

Acid tetrathionate of zinc was prepared from Wackenroder's solution and zinc 
carbonate. 

A definite volume of clear Wackenroder's solution was neutralized with zinc car- 
bonate, and to this a second volume of Wackenroder's solution equal to the first was 
added. The solution was evaporated in a vacuum and the crystalline residue obtained 
separated by filtration, and recrystallized from absolute alcohol by evaporation in a 
vacuum. The salt was dried over sulphuric acid. 

Analysis: A definite weight of the salt was dissolved in water, sodium carbonate 
added, and chlorine passed through the solution. The zinc was determined as the oxide. 
The sulphur was precipitated as the sulphate by the addition of barium chloride. The 
water of crystallization was determined by combustion with lead chromate. The analy- 
sis showed the salt to have the composition Zn(HS4O c )2- 



46 

PREPARATION 

(I) Previous Methods Used. 

Zinc tetrathionate was first prepared by Fordos and Gelis (loc. tit.). 
The general methods used for its preparation are as follows: 

(1) By the action of zinc sulphate on barium tetrathionate. Fordos 
and Gelis (loc. tit.). 

(2) By half neutralizing Wackenroder's solution with zinc carbonate. 
Curtius (loc. tit.); Curtius and Henkel, (loc. tit.). 

The salt prepared by the above investigators in (2) was stated to be the 
acid salt and in solution reacted strongly acid. 

(II) General Procedure of Method Used. 

Zinc tetrathionate was prepared in solution by the method of Fordos 
and Gelis, viz. by mixing in solution equivalent amounts of zinc sulphate 
and barium tetrathionate, and filtering off the barium sulphate formed. 

BaS4Oe.2H2O and ZnSO4.7H2O were weighed out in such equivalent 
amounts as to have 1.0000 gm. of ZnS/Je in solution. They were placed 
in separate beakers, dissolved in small amounts of water and the zinc 
sulphate solution added quantitatively to the solution of barium tetra- 
thionate and allowed to stand for a short time. It was then filtered 
through a Gooch into a test tube within a liter Erlenmeyer filtering flask, 
using a little suction. This solution was neutral to litmus. 

(Ill) Preparation of Barium Tetrathionate. 

The barium tetrathionate was prepared according to the "Suggested 
Method under 'Barium Tetrathionate.' ' 

(IV) Preparation of Zinc Sulphate. 

Baker and Adamson's C. P. zinc sulphate was dissolved in warm water 
at about 35 until a nearly saturated solution was obtained and then 
filtered. The filtrate was placed in a crystallizing dish and allowed to 
cool, during which some of the salt crystallized out. The solution was 
again filtered, the crystallized salt being discarded, and the filtrate placed 
in a crystallizing dish, seeded with a small amount of very finely pulverized 
zinc sulphate and allowed to stand for several days. The very small 
crystals which formed were filtered off, dried between filter paper thor- 



47 

oughly ground in a mortar and placed in a glass stoppered bottle. The 
mother liquor was discarded. 

QUALITATIVE DECOMPOSITION 

1 gram of ZnS 4 O6 was prepared in solution as previously described and 
transferred to an Erlenmeyer flask in such a way that there were 100 cc. 
of solution. 

The Erlenmeyer flask was attached to a Liebig condenser and the solu- 
tion boiled for 24 hours, carbon dioxide being passed through the solution 
during the entire time. Considerable sulphur collected in the condenser 
during the process. 

The odor of sulphur dioxide was easily detected at the mouth of the 
condenser. The evolved gas was passed into bromine water, the excess 
of bromine boiled off, a few drops of hydrochloric acid added and then 
a solution of barium chloride. A white precipitate was formed. 

Negative results were obtained for hydrogen sulphide when tested for 
with lead acetate. 

At the end of the boiling the residue in the condenser was added to the 
flask, the solution filtered, and the residue and filtrate tested qualitatively. 

(I) Residue. 
It was found to consist of sulphur, sulphide being absent. 

(II) Filtrate. 

(1) Sulphate: The solution was tested in the usual way and found 
present. 

(2) Thiosulphate: 

(a) Tested with a solution of ammonium molybdate and concen- 
trated sulphuric acid. Blue ring immediately. 

(b) Tested with iodine solution. 1 drop of N/10 iodine was de- 
colorized by 10 cc. of the solution; two drops gave an iodine color. 

(c) Tested with a dilute solution of potassium permanganate. 
The solution was bleached. 

(3) Sulphite: The sodium nitroprusside-potassium ferrocyanide-zinc 
sulphate tested gave a negative result. 

(4) Trithionate: The mercuric chloride, potassium permanganate, 
mercurous nitrate, and hydrochloric acid tests were applied. Definite 
results were not obtained, but if present it was in very small amounts. 



48 

(5) Pentathionate. 

(a) Tested with ammoniacal silver nitrate. Immediate brown 
precipitate. 

(b) Tested with concentrated potassium hydroxide. Cloudiness 
which does not disappear when made slightly acid with hydrochloric acid. 

(c) Tested with mercurous nitrate. Black precipitate at first, 
but on further addition of the mercurous nitrate the precipitate became 
yellow. 

From the results of the tests given above it may be concluded that the 
following are the final products of decomposition in a boiling solution of 
zinc tetrathionate : sulphate, sulphur dioxide, sulphur and some penta- 
thionate; also a small amount of thiosulphate. 

QUANTITATIVE DECOMPOSITION 

(I) Descriptive. 

The apparatus used, the time of boiling, and the passing of the carbon 
dioxide, were the same as under barium. 

The absorption tubes for the sulphur dioxide were spherical bulbed; 
alkaline hypobromite, which was prepared as previously described under 
barium, was used as the oxidizing agent. 

(II) Procedure. 

1.0000 gm. of zinc tetrathionate was prepared in solution as described 
under "General Procedure of Method Used," transferred quantitatively 
to the Erlenmeyer decomposition flask in such a way that the total volume 
of water used was 100 cc. 

At the end of the boiling the sulphur which had collected in the condenser 
was removed to the decomposition flask, and the solution filtered through 
a hard filter using all necessary precautions. 

(1) The Residue. 

The residue on the filter was washed into a beaker and oxidized by addi- 
tion of bromine using the precautions to obtain and oxidize all the sulphur. 
After the removal of the excess of bromine, the sulphate ion was precipi- 
tated by the addition of a solution of barium chloride using .the necessary 
precautions, and the barium sulphate obtained is designated in the tabel 
as "BaSO 4 From Oxidation of Sulphur." 

(2) The Filtrate. 

The filtrate obtained after the removal of sulphur was heated nearly 



49 

to boiling and a solution of barium chloride used, thus precipitating the 
sulphate ions present. The barium sulphate formed was filtered off 
and is designated in the table as "BaSO4 From Zinc Sulphate." 

The contamination due to the presence of zinc ions as determined by 
dissolving the barium sulphate in hot concentrated sulphuric acid and 
reprecipitating by diluting with water amounted to only about 1 mg. and 
in most of the determinations has been neglected. 

(3) Sulphur Dioxide. 

Sulphur dioxide was determined exactly as described under barium. 

The sulphur content of the sodium hydroxide as found in the blank 
experiment under barium has been applied in each determination. 

TABLE XIII 



Trial. 


Time of 
boiling 
hrs. 


Zinc tet- 
rathionate 
used. 
Gm. 


BaSO 4 
from 
zinc 
sulphate 
Gm. 


BaSO4 from 
oxidation 
of sulphur 
.dioxide. 
Gm. 


BaS0 4 
from 
oxidation 
of sulphur. 
Gm. 


Ratios found to 
ZnSO4 basis 
ZnS04:S0 2 :S. 


1 


8 


1.0000 


0.2426 


0.1216 


0.2248 


1: .501: .927 


2 


8 


1.0000 


0.2399 


0.1925 


0.1811 


1:. 802:. 755 


3 


9.5 


1.0000 


0.2344 


0.2020 


0.2067 


1:.860: .881 


4 


8 


1.0000 


0.2862 


0.2372 


. 2302 


1: .828:. 803 


5 


8 


1.0000 


0.2478 


0.1987 


0.1520 


1:. 800:. 613 



The ratios obtained above do not show that zinc tetrathionate in solu- 
tion decomposes quantitatively into zinc sulphate, sulphur dioxide, and 
two atoms of sulphur. 

The ratios given in the above table were obtained in exactly the same 
way as under Barium in Table XI, except the "Barium Sulphate From 
the Zinc Sulphate" has been converted to an equivalent amount of zinc 
sulphate. 

QUANTITATIVE DECOMPOSITION INCLUDING THE ANALYSIS OF FILTRATES 

As in the case of barium, the boiled solution after the removal of the 
sulphur and the sulphate ions was oxidized with bromine, the excess of 
bromine boiled off and a solution of barium chloride added observing the 
necessary precautions. 

The headings in Table XIV are as follows: 

"BaSO 4 From Decomposition of Zinc Tetrathionate" means, after the 
solution of zinc tetrathionate has been boiled, it is the total barium sul- 
phate obtained from the zinc sulphate, plus that obtained from the oxi- 
dized sulphur dioxide, plus that from the oxidized sulphur. 



50 

"BaSO 4 From Filtrate" means the final filtrate which was oxidized with 
bromine and precipitated with a solution of barium chloride in the usual 
way. 

"Total Amount of BaSC>4 From Same Amount of Zinc Tetrathionate" 
means that 1.0000 gm. of zinc tetrathionate was prepared in solution, 
using the same samples and the same amounts of barium tetrathionate 
and zinc sulphate as were used to prepare the zinc tetrathionate in the 
decomposition flask, oxidized by bromine and precipitated by a solution 
of barium chloride observing precautions previously stated. 

TABLE XIV 









BaSO4 from 
decomposi- 


BaSO 4 


Total 
BaSO4 


Total amt. 
of BaSOi 








Zinc tetra- 


tion of 


from 


found 


from same 


Error 




Time of 


thionate 


zinc tetra- 


ni- 


in an- 


weight 


in 




boiling. 


used. 


thionate. 


trate. 


alyses. 


of zinc tetia- 


BaSO 4 . 


Trial. 


hrs. 


Gm. 


Gm. 


Gm. 


Gm. 


thionate. Gm. 


Gm. 


1 


8 


1.0000 


. 5890 


2.5013 


3.0903 


3 . 0386 


+0.0517 


2 


9.5 


1.0000 


0.6431 


2.4404 


3.0835 


3 . 0386 


+0.0449 


3 


8 


1.0000 


0.7536 


2.2458 


2.9994 


3.0755 


-0.0761 


4 


8 


1.0000 


0.5985 


2.4325 


3.0310 


3.0755 


-0.0445 



The results of Table XIV show that the loss of sulphur dioxide and 
sulphur in the decomposition of the zinc tetrathionate by boiling was 
recovered in the filtrate. 

The ratio of zinc sulphate to sulphur dioxide in Table XIII is about the 
same as barium sulphate to sulphur dioxide in Table XI, while the ratio 
of zinc sulphate to sulphur in Table XIII is less than that of barium sul- 
phate to sulphur in Table XI. 

If there was good evidence of the formation of pentathionate and quite 
probably hexathionate when the barium tetrathionate solution was boiled, 
there is stronger evidence that the higher thionates were formed when 
the zinc tetrathionate solution was boiled, because there was a propor- 
tionately greater loss of sulphur from the boiling solution. 

NICKEL TETRATHIONATE 

BIBLIOGRAPHY 

Kessler, Jour. f. prak. Chem., loc. cit., 36. 

Pogg. Ann. Phys. Chem., loc. cit., 256. 

"Nickel tetrathionate was prepared by mixing equivalent solutions of nickel sul- 
phate and lead tetrathionate and evaporating in a vacuum. The salt was very deli- 
quescent and its solution was practically as stable as solutions of tetrathionic acid." 

The analysis of the salt was not given. 



51 

PREPARATION 

(I) General Procedure of Method Used. 

Nickel tetrathionate was prepared in solution in a way similar to that 
used in the case of the zinc. 

2.000-gm. of BaS 4 O 6 .2H 2 O and 1.322 gm. of NiSO 4 .6H 2 O were weighed 
out, placed in separate beakers and each dissolved in a small amount of 
water. The nickel sulphate solution was then transferred quantitatively 
to the barium tetrathionate solution, allowed to stand a short time and 
filtered exactly as under zinc. 

The solution had a light green color and was neutral to litmus. 
(II) The Barium Tetrathionate and Nickel Sulphate Used. 

The same sample of barium tetrathionate was used as in the case of zinc. 

Ordinary C. P. hydrous nickel sulphate was used. 

QUALITATIVE DECOMPOSITION 

The nickel tetrathionate solution was prepared as described and trans- 
ferred to the Erlenmeyer decomposition flask so that there were 100 cc. 
of water used. The apparatus and procedure were the same as described 
under zinc. 

The solution was boiled for 24 hours and during this time the color 
remained a light green, thus showing that hydrogen sulphide was not 
evolved and nickel sulphide formed. 

During the boiling, sulphur dioxide was given off and sulphur collected 
in the condenser. At the end of the boiling the sulphur in the condenser 
was removed to the decomposition flask and the solution filtered. 

(I) Residue. 
The residue proved to be sulphur. 

(II) Filtrate. 

Tests were made for sulphate, thiosulphate, sulphite, trithionate, and 
pentathionate and the results show the final products in the decomposition 
of a boiling solution of zinc tetrathionate are: sulphate, sulphur dioxide, 
and sulphur; some pentathionate and a small amount of thiosulphate. 

CONCLUSIONS 

Sodium Tetrathionate. 
(1) Sodium tetrathionate was prepared by several similar methods 



52 

and the salt crystallized from water solution by cooling had the highest 
degree of purity. 

(2) The salt crystallized from water solution had the composition 
Na 2 S 4 O6.2H 2 O. 

(3) The yield was considerably increased by preparing the salt according 
to the "Suggested Method." 

(4) The dissociation pressure of the hydrous sodium tetrathionate 
is of such magnitude that the salt should not be dried over concentrated 
sulphuric acid for any considerable time. 

Barium Tetrathionate. 

(1) Barium tetrathionate was prepared and on analysis proved to be 
quite pure, and that crystallized from a water solution had the highest 
degree of purity. 

(2) Practically all the details of the method for its preparation were 
worked out. 

(3) Barium tetrathionate slowly decomposes at the ordinary tempera- 
ture. 

(4) Qualitative decomposition of \ boiling solution showed that the 
final products were sulphate, sulphur dioxide, and sulphur together with 
pentathionate and a trace of thiosulphate. 

(5) Quantitative decomposition of the boiling solution showed that 
secondary reactions occur in the solution forming higher thionates. 

CRYSTALLOGRAPHIC STUDY OF SODIUM AND BARIUM TETRATHIONATE 

(1) Crystals of both sodium and barium tetrathionates were prepared 
from a water solution and some of their optical characteristics determined. 

Zinc Tetrathionate 

(1) A solution of zinc tetrathionate was prepared and it was neutral 
to litmus. 

(2) Qualitative decomposition of the boiling solution showed that the 
final products were sulphate, sulphur dioxide, sulphur and some penta- 
thionate together with small amount of thiosulphate. 

(3) Quantitative analysis of the boiling solution showed that secondary 
reactions occur and that higher thionates were formed to a greater extent 
than in the case of barium. 



53 

Nickel Tetrathionate 

(1) A solution of nickel tetrathionate was prepared; it had a light green 
color and was neutral to litmus. 

(2) Qualitative decomposition of the boiling solution showed that the 
final products were sulphate, sulphur dioxide, sulphur and some penta- 
thionate together with a small amount of thiosulphate. 



ACKNOWLEDGMENT 

The writer desires to express his sincere thanks to Dr. Wm. E. Henderson 
under whose supervision this work was done, and whose advice was most 
helpful at all times and whose interest was inspiring. 

Further, the authors desire to thank Dr. Wm. J. McCaughey, Head of 
the Department of Mineralogy in Ohio State University, for most valuable 
assistance in determining the crystallographic data. 



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